Heat exchanger unit and condensing boiler using the same

ABSTRACT

A heat exchanger unit according to the present invention comprises: a sensible heat exchanger including a sensible heat exchange pipe disposed in a sensible heat exchange area for heating water used for heating by receiving sensible heat generated by a combustion reaction, wherein the sensible heat exchange pipe receives the water used for heating and flows same through the interior, and a sensible heat fin disposed in the sensible heat exchange area, wherein the sensible heat fin is formed in a plate shape across the sensible heat exchange pipe and penetrated by the sensible heat exchange pipe; and a latent heat exchanger positioned downstream from the sensible heat exchange area on the basis of a reference direction, which is a flow direction of combustion gas generated during the combustion reaction, the latent heat exchanger including a latent heat exchange pipe disposed in a latent heat exchange area.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application for patent is a continuation of U.S. patentapplication Ser. No. 16/973,025, filed Dec. 7, 2020, which is theNational Stage of International Application No. PCT/KR2019/006543, filedMay 30, 2019, which claims priority to Korean Patent Application No.10-2018-0064666 filed on Jun. 5, 2018, Korean Patent Application No.10-2018-0064668 filed on Jun. 5, 2018, Korean Patent Application No.10-2018-0064669 filed Jun. 5, 2018, and Korean Patent Application No.10-2018-0156356 filed Dec. 6, 2018.

U.S. patent application Ser. No. 16/973,025, filed on Dec. 7, 2020, andInternational Application No. PCT/KR2019/006543, filed May 30, 2019, areincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to a condensing boiler and a heatexchanger unit used therein.

BACKGROUND ART

A boiler is an apparatus for heating a desired area by heating fluid ina container. Accordingly, to heat up heating-water of the boiler, theboiler generally has a heat source, a burner including the heat source,and a heat exchanger unit for heating the heating-water using combustiongas. In a condensing boiler that comprehensively uses heat of combustiongas, sensible heat generated from a burner is supplied to heating-water,and the sensible heat of the combustion gas generated from the burnerand latent heat caused by a phase change of the combustion gas aresupplied to the heating-water. Accordingly, the heating-water is heated.

To supply the sensible heat and the latent heat to the heating-water, amethod of locating a container for storing the heating-water in aposition close to an area in which the combustion gas flows and a heatsource for supplying sensible heat is mainly used. Heat is indirectlytransferred to the heating-water through the container to raise thetemperature of the heating-water to a temperature appropriate forheating, and thereafter the heating-water is supplied to an area thathas to be heated.

A plate type heat exchanger unit having a plurality of stacked plates ismainly used for the heat transfer. However, the plate type heatexchanger unit has problems of a difficulty in a manufacturing processand high cost despite excellent thermal efficiency.

DISCLOSURE Technical Problem

The present disclosure has been made to solve the above-mentionedproblems occurring in the prior art. An aspect of the present disclosureprovides condensing boiler and a heat exchanger unit used therein thathas excellent thermal efficiency while using a fin-tube type heatexchange device.

Technical Solution

A heat exchanger unit according to an embodiment of the presentdisclosure includes a sensible heat exchanging part including a sensibleheat exchange pipe that is disposed in a sensible heat exchange area forreceiving sensible heat generated by a combustion reaction and heatingheating-water and that receives the heating-water and allows theheating-water to flow therethrough and a sensible heat fin disposed inthe sensible heat exchange area and formed in a plate shape across thesensible heat exchange pipe such that the sensible heat exchange pipepasses through the sensible heat fin, and a latent heat exchanging partincluding a latent heat exchange pipe that is disposed in a latent heatexchange area for receiving latent heat generated during a phase changeof combustion gas and heating the heating-water and that receives theheating-water and allows the heating-water to flow therethrough and alatent heat fin disposed in the latent heat exchange area and formed ina plate shape across the latent heat exchange pipe such that the latentheat exchange pipe passes through the latent heat fin, the latent heatexchange area being located downstream of the sensible heat exchangearea based on a reference direction that is a flow direction of thecombustion gas generated during the combustion reaction.

A condensing boiler according to an embodiment of the present disclosureincludes a burner assembly causes a combustion reaction, a combustionchamber located downstream of the burner assembly on the basis of a flowdirection of a combustion gas generated by the combustion reaction, andin which flame generated by the combustion reaction is located and aheat exchanger unit configured to receive sensible heat and thecombustion gas generated by the combustion reaction to heatheating-water. The heat exchanger unit includes a sensible heatexchanging part including a sensible heat exchange pipe disposed in asensible heat exchange area and configured to receive the heating-waterand allow the heating-water to flow therethrough and a sensible heat findisposed in the sensible heat exchange area and formed in a plate shapeacross the sensible heat exchange pipe such that the sensible heatexchange pipe passes through the sensible heat fin, the sensible heatexchange area being configured to receive sensible heat generated by acombustion reaction and to heat the heating-water, the heat exchangerunit includes a latent heat exchanging part including a latent heatexchange pipe disposed in a latent heat exchange area and configured toreceive the heating-water and allow the heating-water to flowtherethrough and a latent heat fin disposed in the latent heat exchangearea and formed in a plate shape across the latent heat exchange pipesuch that the latent heat exchange pipe passes through the latent heatfin, the latent heat exchange area being located downstream of thesensible heat exchange area based on a reference direction that is aflow direction of combustion gas generated during the combustionreaction and configured to receive latent heat generated during a phasechange of the combustion gas and to heat the heating-water.

Advantageous Effects

Accordingly, heat transfer efficiency may not be deteriorated despitethe use of an inexpensive and easy-to-manufacture fin-tube type heatexchanger unit.

DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical sectional view of part of an exemplary heatexchanger unit.

FIG. 2 is a vertical sectional view of a heat exchanger unit and acondensing boiler using the same according to a first embodiment of thepresent disclosure.

FIG. 3 is a side view of the heat exchanger unit and the condensingboiler using the same according to the first embodiment of the presentdisclosure.

FIG. 4 is a plan view of a combustion chamber of the heat exchanger unitaccording to the first embodiment of the present disclosure.

FIG. 5 is a plan view of a sensible heat exchanger of the heat exchangerunit according to the first embodiment of the present disclosure.

FIG. 6 is a view illustrating an area where a sensible heat exchangepipe and a sensible heat fin are disposed in the vertical sectional viewof the heat exchanger unit according to the first embodiment of thepresent disclosure.

FIG. 7 is a view illustrating an area where a sensible heat exchangepipe and a sensible heat fin are disposed in a vertical sectional viewof a heat exchanger unit according to one modified example of the firstembodiment of the present disclosure.

FIG. 8 is a view illustrating a second general sensible heat side plateof the heat exchanger unit according to the first embodiment of thepresent disclosure and flow passage caps included in a second flowpassage cap plate when viewed from the outside along a predetermineddirection.

FIG. 9 is a view illustrating a first general sensible heat side plateof the heat exchanger unit according to the first embodiment of thepresent disclosure and flow passage caps included in a first flowpassage cap plate when viewed from the inside along the predetermineddirection.

FIG. 10 is a view illustrating a heat exchanger unit according toanother modified example of the first embodiment of the presentdisclosure when viewed from outside a second connection flow passage capplate.

FIG. 11 is a view illustrating a first connection flow passage cap plateof the heat exchanger unit according to the other modified example ofthe first embodiment of the present disclosure.

FIG. 12 is a view illustrating a partial area of a second main generalside plate of the heat exchanger unit according to the other modifiedexample of the first embodiment of the present disclosure together withflow passage caps included in the second connection flow passage capplate when viewed from the outside along a predetermined direction.

FIG. 13 is a view illustrating a first main general side plate of theheat exchanger unit according to the other modified example of the firstembodiment of the present disclosure together with flow passage capsincluded in the first connection flow passage cap plate when viewed fromthe inside along a predetermined direction.

FIG. 14 is a perspective view illustrating a sensible heat flow passageand a latent heat flow passage of the heat exchanger unit according tothe other modified example of the first embodiment of the presentdisclosure.

FIG. 15 is a vertical sectional view of a heat exchanger unit accordingto a second embodiment of the present disclosure.

FIG. 16 is a front view illustrating a flow passage cap plate of a heatexchanger unit according to a modified example of the second embodimentof the present disclosure together with pipes.

FIG. 17 is a vertical sectional view of a heat exchanger unit and acondensing boiler using the same according to a third embodiment of thepresent disclosure.

FIG. 18 is a side view of the heat exchanger unit and the condensingboiler using the same according to the third embodiment of the presentdisclosure.

FIG. 19 is a plan view of the heat exchanger unit according to the thirdembodiment of the present disclosure.

FIG. 20 is a vertical sectional view of the heat exchanger unitaccording to the third embodiment of the present disclosure.

FIG. 21 is a perspective view illustrating a plurality of downstreamfins according to the third embodiment of the present disclosure andcondensate located therebetween.

FIG. 22 is a vertical sectional view of a heat exchanger unit accordingto a first modified example of the third embodiment of the presentdisclosure.

FIG. 23 is a vertical sectional view of a heat exchanger unit accordingto a second modified example of the third embodiment of the presentdisclosure.

FIG. 24 is a vertical sectional view of a heat exchanger unit accordingto a third modified example of the third embodiment of the presentdisclosure.

FIG. 25 is a vertical sectional view of a heat exchanger unit accordingto a fourth modified example of the third embodiment of the presentdisclosure.

FIG. 26 is a view illustrating a second general side plate of the heatexchanger unit according to the third embodiment of the presentdisclosure together with flow passage caps included in the second flowpassage cap plate.

FIG. 27 is a view illustrating a first general side plate of the heatexchanger unit according to the third embodiment of the presentdisclosure together with flow passage caps included in the first flowpassage cap plate.

FIG. 28 is a perspective view illustrating all flow passages included inthe heat exchanger unit according to the third embodiment of the presentdisclosure.

FIG. 29 is a perspective view illustrating a situation in which theconnection flow passage cap plates are separated from each other in theheat exchanger unit according to the other modified example of the firstembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the exemplary drawings. In addingthe reference numerals to the components of each drawing, it should benoted that the identical or equivalent component is designated by theidentical numeral even when they are displayed on other drawings.Further, in describing the embodiment of the present disclosure, adetailed description of well-known features or functions will be ruledout in order not to unnecessarily obscure the gist of the presentdisclosure.

In describing the components of the embodiment according to the presentdisclosure, terms such as first, second, “A”, “B”, (a), (b), and thelike may be used. These terms are merely intended to distinguish onecomponent from another component, and the terms do not limit the nature,sequence or order of the components. When a component is described as“connected”, “coupled”, or “linked” to another component, this may meanthe components are not only directly “connected”, “coupled”, or “linked”but also are indirectly “connected”, “coupled”, or “linked” via a thirdcomponent.

As a method of arranging a burner, heat exchangers, and a combustionchamber constituting a condensing boiler, a method of configuring thecondensing boiler by locating the burner at the lowermost position andsequentially arranging the combustion chamber surrounded by insulationof a dry type, a sensible heat exchanger of a fin-tube type, and alatent heat exchanger of a plate type in an upward direction may beconsidered. This type of condensing boiler is referred to as a bottom-upboiler. In the case of the bottom-up boiler, condensate generated bycondensation of combustion gas in the latent heat exchanger may fallonto the sensible heat exchanger and the combustion chamber. Therefore,the sensible heat exchanger and the insulation of the dry type thatsurrounds the combustion chamber may be easily corroded by thecondensate with high acidity. Furthermore, as the different types ofheat exchangers are connected with each other, manufacturing costs maybe increased due to additional connecting parts.

To solve the problems caused by the condensate, a method of configuringa condensing boiler by locating a burner at the uppermost position andsequentially arranging a combustion chamber thermally insulated by beingsurrounded by a heat insulation pipe, a sensible heat exchanger of afin-tube type, and a latent heat exchanger of a plate type in a downwarddirection may be considered. This type of condensing boiler is referredto as a top-down boiler. In this case, as the latent heat exchanger islocated at the lowermost position, condensate is immediately dischargedthrough a condensate receiver and does not reach the sensible heatexchanger or the combustion chamber, and thus a problem of corrosion maybe solved. However, many parts including the heat insulation pipe usedto cool the combustion chamber are used, and due to this, the number ofassembly steps is increased, which leads to an increase in manufacturingcosts. Furthermore, as the different types of heat exchangers areconnected with each other, manufacturing costs may be increased due toadditional connecting parts.

FIG. 1 is a vertical sectional view of part of an exemplary heatexchanger unit. As illustrated in FIG. 1, a top-down boiler may be used,and a method of performing thermal insulation in a dry type bysurrounding a combustion chamber 102 and a sensible heat exchanger 103with insulation 101 may be considered. That is, a case where theinsulation of a dry type, which is used for the combustion chamber 102,is disposed to insulate heat radiated from the area of the sensible heatexchanger 103 may be considered. However, in this case, due to thesensible heat exchanger 103, flame generated through a combustionreaction, and excessive heat generated from combustion gas, theinsulation 101 may be damaged, and the durability may be decreased.Furthermore, condensate is more likely to be generated in a positionadjacent to the sensible heat exchanger 103 than in the combustionchamber 102, and therefore when the insulation 101, as in the drawing,further extends downward beyond the position that the combustion chamber102 extends downward and reaches, the condensate may make contact withthe insulation 101 of a dry type so that the insulation 101 may bedamaged.

First Embodiment

FIG. 2 is a vertical sectional view of a heat exchanger unit and acondensing boiler 1 using the same according to the first embodiment ofthe present disclosure. FIG. 3 is a side view of the heat exchanger unitand the condensing boiler 1 using the same according to the firstembodiment of the present disclosure.

Referring to the drawings, the heat exchanger unit according to thefirst embodiment of the present disclosure includes a sensible heatexchanger 30, a latent heat exchanger 40, and sensible heat insulationpipes 34. The components constituting the heat exchanger unit may befixed in positions as illustrated.

Furthermore, the condensing boiler 1 including the heat exchanger unitaccording to the first embodiment of the present disclosure includes acombustion chamber 20 and a burner assembly 10 including a burner 11.The burner assembly 10 and the heat exchanger unit are disposed insequence along a flow direction D1 of combustion gas, and components arearranged in the heat exchanger unit along the same direction in theorder of the combustion chamber 20, the sensible heat exchanger 30, thelatent heat exchanger 40, and the sensible heat insulation pipes 34disposed together with the sensible heat exchanger 30. Accordingly, thecomponents of the condensing boiler 1 will be described below in theabove-described order of arrangement.

The heat exchanger unit and the condensing boiler 1 using the sameaccording to the first embodiment of the present disclosure will bedescribed below based on a top-down condensing boiler 1 in whichcombustion gas flows vertically downward. Accordingly, the flowdirection D1 of the combustion gas that is represented by an arrow maybe the same as the vertical downward direction at the position where thecondensing boiler 1 is installed. As the top-down condensing boiler 1 isselected, condensate produced by condensation of the combustion gas maybe generated only at the lowermost side of the condensing boiler 1 andmay be immediately discharged to the outside through a lower end of thecondensing boiler 1. Accordingly, components constituting the condensingboiler 1 may be prevented from being corroded. However, theconfiguration of the present disclosure may be used for a bottom-upcondensing boiler capable of naturally forming a path of heating-waterin a downward direction by using a property by which heated combustiongas is moved upward by convection.

The condensing boiler 1 according to the first embodiment of the presentdisclosure may include a condensate receiver 55 located at the mostdownstream side along the flow direction D1 of the combustion gas. Whencondensate generated from the latent heat exchanger 40 drops in thevertically downward direction by the weight of the condensate, thecondensate receiver 55 may collect the condensate. To allow thecollected condensate to be discharged through a condensate outlet 53extending in the vertically downward direction, the condensate receiver55 may have an inner surface inclined toward the condensate outlet 53.

Furthermore, to allow residual combustion gas to be discharged at thesame time that the condensate is discharged, an exhaust duct 52 may beformed so as to be in communication with the condensate receiver 55. Theexhaust duct 52 extends in the vertically upward direction anddischarges the residual combustion gas to the outside.

Burner Assembly 10

The burner assembly 10 is a component that includes the burner 11radiating heat and that causes a combustion reaction of injected fueland air to generate combustion gas.

A premix burner may be used as the burner assembly 10 used in thecondensing boiler 1 according to the first embodiment of the presentdisclosure. The premix type burner is a device that mixes injected airand fuel at a predetermined ratio and burns the mixed air and fuel usingradiating heat to generate combustion gas. For this operation, theburner assembly 10 according to the first embodiment of the presentdisclosure may include a mix chamber 12 that is a space in which mixedfuel for a combustion reaction is prepared by mixing injected fuel andair at a predetermined ratio, and the burner 11 that applies heat to themixed fuel mixed by the mix chamber 12. The burner assembly 10 havingthe above-described structure is provided to obtain optimal fuelefficiency and thermal efficiency by causing a combustion reaction byheating air and fuel mixed at a ratio appropriate for the combustionreaction.

To supply air into the mix chamber 12 and blow combustion gas generatedin the burner assembly 10 in the vertically downward direction, thecondensing boiler 1 of the present disclosure may further include ablower 54. The blower 54 may include a pump that is connected with themix chamber 12 and that forcibly delivers air toward the burner assembly10 that is connected to the mix chamber 12 in the vertically downwarddirection.

Combustion Chamber 20

FIG. 4 is a plan view of the combustion chamber 20 according to thefirst embodiment of the present disclosure.

The combustion chamber 20 will be described below with reference to FIG.4 together with FIGS. 2 and 3. The combustion chamber 20 is a componentthat includes an interior space 22 provided such that flame that acombustion reaction by the burner assembly 10 generates is located.Accordingly, the combustion chamber 20 is formed by surrounding theinterior space 22 with sidewalls. The burner assembly 10 and thecombustion chamber 20 are coupled such that the burner 11 of the burnerassembly 10 is located upstream of the interior space 22 based on theflow direction D1 of the combustion gas.

The burner assembly 10 applies heat to air and fuel to cause acombustion reaction. Flame and combustion gas accompanied by thermalenergy are generated as products of the combustion reaction. The flameis located in the interior space 22 of the combustion chamber 20, butextends from the burner assembly 10 along the flow direction D of thecombustion gas. The combustion gas flows through the interior space 22.The interior space 22 of the combustion chamber 20 may be connected in adirection parallel to the flow direction D1 of the combustion gas. Inthe first embodiment of the present disclosure, the flow direction D1 ofthe combustion gas is the vertically downward direction, and thereforethe interior space 22 of the combustion chamber 20 is formed to beconnected in the vertical direction.

A combustion chamber heat insulation part 24 may be formed on at least apartial area of an inner surface of a combustion chamber sidewall 21constituting the combustion chamber 20. The combustion chamber sidewall21 may be constituted by two general side plates 211 parallel to eachother and two heat insulation side plates 212 perpendicular to thegeneral side plates 211 and parallel to each other and may be formed ina rectangular parallelepiped shape. The combustion chamber heatinsulation part 24 may be disposed on the insides of the heat insulationside plates 212. The combustion chamber heat insulation part 24 may beformed of insulation blocking a heat flow and may reduce the amount bywhich heat generated by the combustion reaction is transferred outsidethe combustion chamber 20 through inner surfaces of the combustionchamber 20. The amount of heat transferred from the interior space 22 ofthe combustion chamber 20 to the outside of the combustion chamber 20may be reduced by the combustion chamber heat insulation part 24. Aporous polystyrene panel decreasing a heat flow or a needle mat made ofsilica, which is an inorganic material, may be used as an example of theinsulation. However, the type of the insulation is not limited thereto.

The combustion chamber heat insulation part 24 may be disposed on thegeneral side plates 211 of the combustion chamber 20 as well, and thusan additional thermal insulation effect may be obtained by surroundingthe entire interior space 22 of the combustion chamber 20 with theinsulation.

A heat insulation pipe through which fluid flows may be disposed aroundthe combustion chamber 20 for thermal insulation. However, in a casewhere a large number of heat insulation pipes are used, a lot of cost isconsumed in production. However, because the heat exchanger unit of thepresent disclosure is implemented in the top-down type, condensation ofcondensate does not occur in the combustion chamber 20, and there is norisk of corrosion. Accordingly, the combustion chamber 20 of a dry typethat uses insulation cheaper than a heat insulation pipe as a materialof which the combustion chamber heat insulation part 24 is made may beconfigured.

The length of the combustion chamber heat insulation part 24 may bedetermined such that the combustion chamber heat insulation part 24surrounds only the interior space 22 of the combustion chamber 20without surrounding the sensible heat exchanger 30, which will bedescribed below, based on the flow direction D1 of the combustion gas.That is, the combustion chamber heat insulation part 24 may be providedso as not to be located inside a sensible heat exchanger case 31 thatwill be described below. Accordingly, in the case where the insulation101 is disposed as illustrated in FIG. 1, the insulation 101 may bedamaged by excessive heat and condensate, whereas in the firstembodiment of the present disclosure, the combustion chamber heatinsulation part 24 is disposed as illustrated in FIG. 2, and thusexcessive heat generated from the sensible heat exchanger 30 may not betransferred to the combustion chamber heat insulation part 24.

Sensible Heat Exchanger 30

FIG. 5 is a plan view of the sensible heat exchanger 30 of the heatexchanger unit according to the first embodiment of the presentdisclosure. FIG. 6 is a view illustrating an area where a sensible heatexchange pipe 32 and a sensible heat fin 33 are disposed in the verticalsectional view of the heat exchanger unit according to the firstembodiment of the present disclosure.

A basic configuration of the sensible heat exchanger 30 will bedescribed below with reference to FIGS. 2, 3, 5, and 6.

The sensible heat exchanger 30 is disposed downstream of the combustionchamber 20 based on the flow direction D1 of the combustion gas. Thesensible heat exchanger 30 is a component that receives, by radiant heatand convection of the combustion gas, sensible heat generated by acombustion reaction triggered by the burner assembly 10 located over thesensible heat exchanger 30 and that heats heating-water flowing in thesensible heat exchanger 30.

Specifically, the sensible heat exchanger 30 includes the sensible heatexchange pipe 32 through which the heating-water flows and around whichthe combustion gas flows, and the sensible heat exchanger case 31 intowhich opposite ends of the sensible heat exchange pipe 32 are inserted.The sensible heat exchange pipe 32 is located in the sensible heatexchanger case 31, and the combustion gas flows around the sensible heatexchange pipe 32 to indirectly exchange heat with the heating-water.

The sensible heat exchange pipe 32 extends along a predetermineddirection D2 in a space formed in the sensible heat exchanger case 31.The predetermined direction D2 may preferably be a directionperpendicular to the flow direction D1 of the combustion gas. Thesensible heat exchange pipe 32 may include a plurality of straightportions 321, 322, 323, and 324 arranged to be spaced apart from eachother along an orthogonal direction perpendicular to the one directionand the flow direction D1 of the combustion gas.

The plurality of straight portions 321, 322, 323, and 324 are arranged,and flow passage cap plates 361 and 362 that will be described belowexist to connect end portions of the straight portions 321, 322, 323,and 324 inserted into insertion holes formed in general sensible heatside plates 311 of the sensible heat exchanger case 31 that will bedescribed below. The set of the straight portions 321, 322, 323, and 324forms the one sensible heat exchange pipe 32. Accordingly, a continuouswinding flow passage of the heating-water may be formed by thearrangement of the sensible heat exchange pipe 32.

For example, in a case where the straight portions 321, 322, 323, and324 of FIG. 5 are connected in series, the heating-water may be heatedby receiving sensible heat of the combustion gas and the burner assembly10 while passing through the sensible heat exchange pipe 32 in such amanner that the heating-water introduced in the direction of the arrowillustrated in FIG. 5 is discharged by flowing to the right in thedrawing along the first outer straight portion 321 included in thesensible heat exchange pipe 32, flowing to the left in the drawing alongthe intermediate straight portion 323 located under the first outerstraight portion 321 in the drawing, flowing, in a discharge step, tothe right in the drawing along the intermediate straight portion 324located over the second outer straight portion 322 in the drawing, andmoving to the left in the drawing along the second outer straightportion 322.

A turbulator (not illustrated) having a shape that hampers a flow of theheating-water to make the flow of the heating-water turbulent may bedisposed in the sensible heat exchange pipe 32.

The sensible heat exchanger case 31 may be constituted by two generalside plate portions spaced apart from each other in the predetermineddirection D2 and parallel to each other and two heat insulation sideplate portions spaced apart from each other along an orthogonaldirection perpendicular to the predetermined direction D2 and parallelto each other and may be formed in the form of a rectangularparallelepiped. The general side plate portions and the heat insulationside plate portions may be general side plates and heat insulation sideplates that are separate from each other and may be partial areas of aside plate of an integrated heat exchanger case. In this disclosure, itwill be exemplified that the general side plate portions and the heatinsulation side plate portions are formed of general side plates andheat insulation side plates that are separate from each other.

The general sensible heat side plates 311 and sensible heat insulationside plates 312 form the interior space of the sensible heat exchangercase 31. Here, the sensible heat insulation side plates 312 are usedwith the meaning of side plates to which the sensible heat insulationpipes 34 are disposed to be adjacent, rather than the meaning of sideplates that reduce the amount of heat transferred to the outside,thereby achieving thermal insulation.

The general sensible heat side plates 311 may include a first generalsensible heat side plate 3111 and a second general sensible heat sideplate 3112 spaced apart from each other along the predetermineddirection D2. The opposite ends of the straight portions 321, 322, 323,and 324 constituting the sensible heat exchange pipe 32 may be insertedinto the first general sensible heat side plate 3111 and the secondgeneral sensible heat side plate 3112, and thus the straight portions321, 322, 323, and 324 may be accommodated in the sensible heatexchanger case 31. The combustion gas flows in the space formed in thesensible heat exchanger case 31 and moves from the combustion chamber 20to a latent heat exchanger case 41 that will be described below.

The sensible heat insulation pipes 34 may be disposed adjacent to thesensible heat exchanger 30. The sensible heat insulation pipes 34 arepipe type components that are disposed to thermally insulate thesensible heat exchanger 30 by allowing the heating-water to flow throughthe components. Here, the thermal insulation includes both confiningheat in any position to prevent heat transfer and absorbing heatreleased from any position to the outside so as to decrease the amountof heat finally released to the outside. The meaning of the thermalinsulation may be identically applied to other embodiments of thepresent disclosure and modified examples thereof.

Specifically, the sensible heat insulation pipes 34 may be disposedadjacent to the outsides of the sensible heat insulation side plates312. The sensible heat insulation pipes 34 may be disposed adjacent tothe two sensible heat insulation side plates 312, respectively. Thesensible heat insulation pipes 34 may be disposed to make contact withthe outsides of the sensible heat insulation side plates 312, or thesensible heat insulation pipes 34 may be disposed in positions spacedapart from the outsides of the sensible heat insulation side plates 312.

Referring to the drawings, in the heat exchanger unit according to thefirst embodiment of the present disclosure, a first sensible heatinsulation pipe 341 and a second sensible heat insulation pipe 342 arespaced apart from each other and are disposed along the outsides of thesensible heat insulation side plates 312. In FIG. 5, the sensible heatinsulation pipes 34 are illustrated as being located inward of thesensible heat insulation side plates 312. However, the sensible heatinsulation side plates 312 cover the sensible heat insulation pipes 34at the same time as being located inward of the sensible heat insulationpipes 34 inside the sensible heat exchanger 30, and the positions of thesensible heat insulation pipes 34 are illustrated for convenience ofdescription. Accordingly, the sensible heat insulation pipes 34 coveredby the sensible heat insulation side plates 312 are actually located inthe area where the sensible heat insulation pipes 34 are illustrated inFIG. 5, and in the plan view, the sensible heat insulation pipes 34 donot appear.

Accordingly, the sensible heat insulation pipes 34 are located outsidethe sensible heat exchanger case 31 through which the combustion gaspasses, and therefore the sensible heat insulation pipes 34 may notcross or meet the combustion gas. The sensible heat insulation pipes 34may not be used for heat exchange between the combustion gas and theheating-water, but may perform only a thermal insulation function ofblocking release of heat from the sensible heat exchanger 30 to theoutside by using the heating-water.

The sensible heat insulation pipes 34 may be disposed to be spaced apartfrom the combustion chamber 20 along the flow direction D1 of thecombustion gas without making contact with the combustion chamber 20.Accordingly, the sensible heat insulation pipes 34 may not be used forthermal insulation of the combustion chamber 20, but may be used onlyfor thermal insulation of the sensible heat exchanger 30.

The sensible heat insulation pipes 34, together with the sensible heatexchange pipe 32, form a sensible heat flow passage through which theheating-water flows.

The shape of interior spaces of the sensible heat insulation pipes 34,as illustrated in FIGS. 2 and 6, may be formed in an oval shape in across-section obtained by cutting the sensible heat insulation pipes 34with a plane perpendicular to the direction in which the sensible heatinsulation pipes 34 extend. Specifically, the interior spaces of thesensible heat insulation pipes 34 may be formed in an oval shape havinga long axis parallel to the flow direction D1 of the combustion gas.

The sensible heat insulation pipes 34 may be located adjacent to thesensible heat insulation side plates 312 of the sensible heat exchanger30 and may be disposed at an upstream side based on the flow directionD1 of the combustion gas. That is, the sensible heat insulation pipes 34may be disposed closer to the combustion chamber 20 than the latent heatexchanger 40 that will be described below. Flame generated by the burnerassembly 20 in the combustion chamber 20 may reach downstream of thecombustion chamber 20 based on the flow direction D1 of the combustiongas, and therefore the upstream side of the sensible heat exchanger 30may have a highest temperature while making contact with the combustionchamber 20. Accordingly, the sensible heat insulation pipes 34 may bedisposed adjacent to the upstream side of the sensible heat exchanger 30and may thermally insulate the upstream side of the sensible heatexchanger 30 from which a large amount of heat is released due to thelargest temperature difference between the interior space of thesensible heat exchanger 30 and the outside. However, the sensible heatinsulation pipes 34 may be located in the center based on the flowdirection D1 of the combustion gas.

The sensible heat exchanger 30 may further include the sensible heat fin33 capable of raising the thermal conductivity of the sensible heatexchange pipe 32, and thus the sensible heat exchanger 30 of a fin-tubetype may be formed. The sensible heat fin 33 is formed in a plate shapethat is perpendicular to the direction in which the sensible heatexchange pipe 32 extends, and the sensible heat exchange pipe 32 passesthrough the sensible heat fin 33. A plurality of sensible heat fins 33may be disposed to be spaced apart from each other at predeterminedintervals along the predetermined direction D2 in which the sensibleheat exchange pipe 32 extends. The sensible heat exchange pipe 32 andthe sensible heat fin 33 may be formed of a metallic material with highthermal conductivity to increase the surface area of the sensible heatexchange pipe 32 from which the sensible heat fin 33 receives sensibleheat, thereby transferring a larger amount of sensible heat to theheating-water.

In a cross-section obtained by cutting the sensible heat exchange pipe32 with a plane perpendicular to the predetermined direction D2 in whichthe sensible heat exchange pipe 32 extends, the interior space of thesensible heat exchange pipe 32 may be formed in the shape of a long holethat extends along the flow direction D1 of the combustion gas. As canbe seen in FIG. 6, the sensible heat exchange pipe 32 according to thefirst embodiment of the present disclosure may have a flat long holeshape formed such that a value obtained by dividing the length of theinterior space of the sensible heat exchange pipe 32 in thecross-section based on the flow direction D1 of the combustion gas bythe width according to the direction perpendicular to the flow directionD1 of the combustion gas equals 2 or more.

When the flat type pipe having the above-described shape is employed forthe sensible heat exchange pipe 32, due to a wider heat exchange area inthe relationship with combustion gas, the heating-water may receive alarger amount of heat and may be sufficiently heated even though flowingalong the sensible heat exchange pipe 32 having the same length, ascompared with when a pipe having a different shape, such as a circularshape or an oval shape, is employed for the sensible heat exchange pipe32.

A through-hole through which the sensible heat exchange pipe 32 passesmay be formed in the sensible heat fin 33. The area of the through-holemay be equal to or smaller than the area of the sensible heat exchangepipe 32, and the sensible heat exchange pipe 32 may be firmly insertedinto the through-hole. Furthermore, the sensible heat fin 33 may beintegrally coupled with the sensible heat exchange pipe 32 throughbrazing welding.

However, the sensible heat insulation pipes 34 are not coupled with thesensible heat fin 33. The sensible heat insulation pipes 34 are notfastened with the sensible heat fin 33, and the sensible heat insulationpipes 34 and the sensible heat fin 33 may be disposed on opposite sideswith the sensible heat insulation side plates 312 therebetween. Thesensible heat fin 33 and the sensible heat insulation pipes 34 may makecontact with the sensible heat insulation side plates 312, but thesensible heat fin 33 and the sensible heat insulation pipes 34 do notmake direct contact with each other. Because the sensible heatinsulation pipes 34, as described above, are disposed for thermalinsulation of the sensible heat exchanger 30 rather than for heatexchange between the combustion gas and the heating-water, the sensibleheat fin 33 and the sensible heat insulation pipes 34 are not directlyconnected with each other. Accordingly, the sensible heat fin 33 and thesensible heat insulation pipes 34 are disposed so as not to cross eachother.

A common louver hole 331 may be additionally formed in the sensible heatfin 33 along the predetermined direction D2 in which the sensible heatexchange pipe 32 extends. The louver hole 331 may be formed by punching.The louver hole 331 includes a burr raised along the periphery thereof.When the combustion gas flows, the burr blocks the combustion gas tocause the combustion gas to flow around the sensible heat exchange pipe32, thereby facilitating heat exchange between the combustion gas andthe heating-water.

A plurality of louver holes 331 may be formed. The louver holes 331, asillustrated in FIG. 6, may include a plurality of first louver holes3311 that extend in an oblique direction with respect to the flowdirection D1 of the combustion gas and that are formed in the outermostportions of the sensible heat fin 33, and a plurality of second louverholes 3312 that are formed between the sensible heat exchange pipes 32adjacent to each other and that extend in the direction perpendicular tothe flow direction D1 of the combustion gas. The louver holes 331 may bedisposed to be spaced apart from each other at predetermined intervalsalong the flow direction D1 of the combustion gas.

The sensible heat fin 33 may further include valleys 334 and protrudingportions 333. The sensible heat fin 33 may be basically formed tosurround the sensible heat exchange pipe 32. The sensible heat fin 33may surround areas corresponding to a predetermined width from theperipheries of upstream-side end portions of the sensible heat exchangepipe 32 based on the flow direction D1 of the combustion gas such thatthe areas are distinguished from the remaining areas of the sensibleheat exchange pipe 32. Accordingly, between the adjacent upstream-sideend portions of the sensible heat exchange pipe 32, the valleys 334 maybe concavely formed in the sensible heat fin 33 along the flow directionD1 of the combustion gas. The areas of the sensible heat fin 33 that areadjacent to the upstream-side end portions of the sensible heat exchangepipe 32 relatively protrude to form the protruding portions 33.Unnecessary areas are open by forming the valleys 334, and thus thecombustion gas may more freely flow between the sensible heat fin 33 andthe sensible heat exchange pipe 32.

The sensible heat fin 33 may further include concave portions 332. Theconcave portions 332 are concavely formed from a downstream-side edge ofthe sensible heat fin 33 toward downstream-side end portions of thesensible heat exchange pipe 32 based on the flow direction D1 of thecombustion gas. The purpose of forming the concave portions 332 issimilar to the purpose of forming the valleys 334.

According to one modified example of the first embodiment, the shapes ofa sensible heat exchange pipe 62, sensible heat insulation pipes 64, anda sensible heat fin 63 may be deformed. FIG. 7 is a view illustrating anarea where the sensible heat exchange pipe 62 and the sensible heat fin63 are disposed in a vertical sectional view of a heat exchanger unitaccording to the one modified example of the first embodiment of thepresent disclosure.

According to the one modified example of the first embodiment, thesensible heat insulation pipes 64 may be disposed adjacent to anupstream side of a sensible heat exchanger 60 based on the flowdirection of the combustion gas, which is one of directions in which thecross-section of the illustrated sensible heat exchange pipe 62 extends,and a cross-section obtained by cutting the sensible heat insulationpipes 64 with a plane perpendicular to a predetermined direction inwhich the sensible heat insulation pipes 64 extend may have a circularshape. Furthermore, unlike in FIG. 6, the sensible heat insulation pipes64 may be disposed adjacent to an inner surface of a heat insulationside plate 65. Unlike in the first embodiment of FIG. 6, six sensibleheat exchange pipes 62 may be provided in the one modified example ofthe first embodiment of FIG. 7. However, the number of sensible heatexchange pipes 62 is not limited thereto.

According to the one modified example of the first embodiment, likewiseto second louver holes 6312, first louver holes 6311 of the sensibleheat fin 63 may extend in a direction perpendicular to the flowdirection of the combustion gas. Various modifications can be made tothe shape of louver holes 631.

The flow passage cap plates 361 and 362 of the sensible heat exchanger30 according to the first embodiment will be described below withreference to FIGS. 2, 3, 5, 6, 8, and 9. FIG. 8 is a view illustratingthe second general sensible heat side plate 3112 according to the firstembodiment of the present disclosure and flow passage caps included inthe second flow passage cap plate 362 when viewed from the outside alongthe predetermined direction D2. FIG. 9 is a view illustrating the firstgeneral sensible heat side plate 3111 of the heat exchanger unitaccording to the first embodiment of the present disclosure and flowpassage caps included in the first flow passage cap plate 361 whenviewed from the inside along the predetermined direction D2.

Referring to FIG. 29 for explaining another modified example of thefirst embodiment of the present disclosure, FIG. 8 is view in which flowpassage caps 3621, 3622, and 3623 of the second flow passage cap plate362 are illustrated by dotted lines on a view of the second generalsensible heat side plate 3112, the straight portions 321, 322, 323, and324 of the sensible heat exchange pipe 32, and the sensible heatinsulation pipes 341 and 342 of the first embodiment of the presentdisclosure that corresponds to a view of a second main general sideplate 5112 and pipes 32, 42, 341, and 342 coupled thereto when viewedfrom a second connection flow passage cap plate 72 of FIG. 29 along lineH-H′. FIG. 9 is a view in which flow passage caps 3611 and 3612 of thefirst flow passage cap plate 361 are illustrated by dotted lines on aview of the first general sensible heat side plate 3111, the straightportions 321, 322, 323, and 324 of the sensible heat exchange pipe 32,and the sensible heat insulation pipes 341 and 342 of the firstembodiment of the present disclosure that corresponds to a view of afirst main general side plate 5111, into which a first connection flowpassage cap plate 71 is inserted, when viewed along line G-G′ of FIG. 29for explaining the other modified example of the first embodiment of thepresent disclosure.

The heat exchanger unit may include the plurality of flow passage capplates 361 and 362 including a plurality of flow passage caps thatconnect the sensible heat insulation pipes 34 and end portions of thesensible heat exchange pipe 32 adjacent to the sensible heat insulationpipes 34 or connect the straight portions 321, 322, 323, and 324adjacent to each other among the plurality of straight portions 321,322, 323, and 324. The flow passage cap plates 361 and 362 may includethe flow passage caps and may connect the straight portions 321, 322,323, and 324 spaced apart from each other, thereby forming a flowpassage through which the heating-water flows in the sensible heatexchanger 30.

Specifically, opposite ends of the straight portions 321, 322, 323, and324 included in the sensible heat exchange pipe 32 and opposite ends ofthe sensible heat insulation pipes 34 are inserted into the generalsensible heat side plates 311 of the sensible heat exchanger case 31,but are open without being closed. The straight portions 321, 322, 323,and 324 included in the sensible heat exchange pipe 32 and the sensibleheat insulation pipes 34 extend from one of the general sensible heatside plates 311 to the other, and the opposite ends thereof are exposedoutside the general sensible heat side plates 311. The flow passage capplates 361 and 362 are coupled to the general sensible heat side plates311 while covering the general sensible heat side plates 311 from theoutside. Accordingly, the flow passage caps of the flow passage capplates 361 and 362, together with the general sensible heat side plates311, form a connection space that surrounds the ends of the straightportions 321, 322, 323, and 324 and the ends of the sensible heatinsulation pipes 34.

The flow passage caps included in the flow passage cap plates 361 and362 form an empty connection space, in which fluid is able to flow,between the general sensible heat side plates 311 and the inner surfacesof the flow passage caps. The flow passage caps having the connectionspace therein may connect two straight portions adjacent to each otheramong the plurality of straight portions 321, 322, 323, and 324 insertedinto the general sensible heat side plates 311, or may connect thesensible heat insulation pipes 34 and straight portions adjacent to thesensible heat insulation pipes 34. The flow passage cap plates 361 and362 may be coupled to the general sensible heat side plates 311 throughbrazing welding, or may be fit into the general sensible heat sideplates 311. However, the coupling method is not limited thereto.

The number of straight portions 321, 322, 323, and 324 or the sensibleheat insulation pipes 34 that the flow passage caps simultaneouslyconnect is not limited to the content illustrated in the drawing.Accordingly, the number of flow passage caps included in one flowpassage cap plate 361 or 362 is also not limited to the contentillustrated, and a modification can be made to the number of flowpassage caps.

A flow passage cap may form a series flow passage in which an inlet ofone pipe and an outlet of another pipe are connected, or may form aparallel flow passage in which inlets and outlets of connected pipes arecommon. Here, an inlet refers to an opening at one end of a pipe throughwhich the heating-water is introduced into the pipe, and an outletrefers to an opening at an opposite end of the pipe through which theheating-water is released from the pipe. The pipes include the straightportions 321, 322, 323, and 324 and the first and second sensible heatinsulation pipes 341 and 342. In a case of forming a series flow passageusing the pipes, acoustic boiling noise generated by the heating-waterthat flows slow and is overheated may be reduced, and the heating-watermay be allowed to flow fast. In a case where a parallel flow passage isat least partially included in the series flow passage, the load of apump forcibly delivering the heating-water may be decreased.

A straight portion in which one end of the sensible heat exchange pipe32 is located and that is located at the outermost position based on theorthogonal direction is referred to as the first outer straight portion321. A sensible heat insulation pipe adjacent to the first outerstraight portion 321 is referred to as the first sensible heatinsulation pipe 341.

Furthermore, a sensible heat insulation pipe located on the oppositeside to the first sensible heat insulation pipe 341 in the orthogonaldirection is referred to as the second sensible heat insulation pipe342, a straight portion adjacent to the second sensible heat insulationpipe 342 is referred to as the second outer straight portion 322, andstraight portions located between the first outer straight portion 321and the second outer straight portion 322 are referred to as theintermediate straight portions 323 and 324.

The first sensible heat insulation pipe 341, the first outer straightportion 321, the intermediate straight portions 323 and 324, the secondouter straight portion 322, and the second sensible heat insulation pipe342 may be sequentially connected to form one series sensible heat flowpassage, or may form a parallel flow passage in which inlets and outletsof at least some thereof are common. One intermediate straight portion323 and the other intermediate straight portion 324 may also beconnected in series.

The pipes may be connected only in series to form a sensible heat flowpassage. For example, inlets and outlets of pipes adjacent to each otheramong the pipes may be connected in series to form a sensible heat flowpassage through which the heating-water is delivered from the firstsensible heat insulation pipe 341 to the first outer straight portion321, the intermediate straight portion 323 adjacent to the first outerstraight portion 321, the intermediate straight portion 324 adjacent tothe second outer straight portion 322, the second outer straight portion322, and the second sensible heat insulation pipe 342 in sequence. Asensible heat flow passage configured only in series will be describedbelow in detail in the description of a sensible heat flow passageincluded in a heat exchanger unit according to another modified exampleof the first embodiment of the present disclosure that will be describedwith reference to FIGS. 10 to 14.

A sensible heat flow passage may partly include a parallel flow passage,and therefore a case where some of the straight portions 321, 322, 323,and 324 are connected in parallel will be described in the descriptionof a sensible heat flow passage according to an embodiment of thepresent disclosure that is described with reference to FIGS. 8 and 9.

For example, a parallel flow passage may be configured as follows. Thefirst sensible heat insulation pipe 341 and the first outer straightportion 321 may form a parallel flow passage, the second sensible heatinsulation pipe 342 and the second outer straight portion 322 may form aparallel flow passage, the intermediate straight portions 323 and 324may form a parallel flow passage, the first outer straight portion 321and the intermediate straight portion 323 may form a parallel flowpassage, and the second outer straight portion 322 and the intermediatestraight portion 324 may form a parallel flow passage.

Furthermore, an entire sensible heat flow passage may be configured bycombining a plurality of parallel flow passages among the parallel flowpassages with a series flow passage. For example, when the firstsensible heat insulation pipe 341 and the first outer straight portion321 form a parallel flow passage, the parallel flow passage, theintermediate straight portions 323 and 324, the second outer straightportion 322, and the second sensible heat insulation pipe 342 may besequentially connected to form one sensible heat flow passage. Incontrast, when the second sensible heat insulation pipe 342 and thesecond outer straight portion 322 form a parallel flow passage, thefirst sensible heat insulation pipe 341, the first outer straightportion 321, the intermediate straight portions 323 and 324, and theparallel flow passage may be sequentially connected to form one sensibleheat flow passage. Furthermore, in a case where parallel flow passagesare formed in the above-described two portions, the parallel flowpassages may be connected with the intermediate straight portions 323and 324 located therebetween to form one sensible heat flow passage.

A case where a parallel flow passage receives the heating-water firstwhen the heating-water is introduced into the sensible heat exchanger 30will be described in the first embodiment of the present disclosure. Thefirst outer straight portion 321 and the first sensible heat insulationpipe 341 may be connected in parallel and may receive and discharge theheating-water together. A heating-water supply hole 371 may be formed inthe inlet flow passage cap 3621 among the flow caps included in thesecond flow passage cap plate 362 that covers the second generalsensible heat side plate 3112. The heating-water supply hole 371 may bean opening that receives the heating-water from a heating-water pipe anddelivers the heating-water to the inlet flow passage cap 3621. Theheating-water supply hole 371 may connect a sensible heat flow passageand a latent heat flow passage by receiving the heating-water dischargedfrom the latent heat exchanger 40.

The inlet flow passage cap 3621 connects one end of the first outerstraight portion 321 and one end of the first sensible heat insulationpipe 341 that is adjacent to the one end of the first outer straightportion 321. While the heating-water is supplied to the inlet flowpassage cap 3621 through the heating-water supply hole 371, theheating-water is introduced into the one end of the first outer straightportion 321 and the one end of the first sensible heat insulation pipe341 that are connected to the inlet flow passage cap 3621.

The heating-water passes through the first outer straight portion 321and the first sensible heat insulation pipe 341 and reaches the firstflow passage cap 3611 of the first flow passage cap plate 361 located onthe opposite side to the second flow passage cap plate 362 based on thesensible heat exchange pipe 32. The first flow passage cap 3611 connectsan opposite end of the first sensible heat insulation pipe 341, anopposite end of the first outer straight portion 321, and theintermediate straight portion 323 adjacent to the first outer straightportion 321. Accordingly, the first outer straight portion 321 and thefirst sensible heat insulation pipe 341 is connected with the adjacentintermediate straight portion 323 in series in the first flow passagecap 3611 and receives the heating-water passing through the first outerstraight portion 321 and the first sensible heat insulation pipe 341.

The intermediate straight portion 323 adjacent to the first outerstraight portion 321 and the intermediate straight portion 324 adjacentto the second outer straight portion 322 that will be described belowmay be connected in the intermediate flow passage cap 3623 located onthe second flow passage cap plate 362 and may deliver the heating-waterfrom one intermediate straight portion 323 to the other intermediatestraight portion 324. The two intermediate straight portions 323 and 324form part of a heating-water flow passage in series in the intermediateflow passage cap 3623.

A case where the heating-water is discharged through a parallel flowpassage from the sensible heat exchanger 30 will be described. Astraight portion disposed adjacent to the second sensible heatinsulation pipe 342, which is the sensible heat insulation pipe 34through which the heating-water is discharged, is the second outerstraight portion 322.

The second outer straight portion 322 and the second sensible heatinsulation pipe 342 may be connected in parallel and may receive anddischarge the heating-water together. One end of the second outerstraight portion 322 and one end of the second sensible heat insulationpipe 342 that is adjacent to the one end of the second outer straightportion 322 are connected with the straight portion 324 adjacent to thesecond outer straight portion 322 in series in the second flow passagecap 3621 among the flow passage caps included in the first flow passagecap plate 361 that covers the first general sensible heat side plate3111. Accordingly, the heating-water delivered to the second flowpassage cap 3612 through the adjacent straight portion 324 is introducedinto the one end of the second outer straight portion 322 and the oneend of the second sensible heat insulation pipe 342.

The heating-water passes through the second outer straight portion 322and the second sensible heat insulation pipe 342 and is discharged to anopposite end of the second outer straight portion 322 and an oppositeend of the second sensible heat insulation pipe 342. The opposite end ofthe second outer straight portion 322 and the opposite end of the secondsensible heat insulation pipe 342 are connected to the outlet flowpassage cap 3622, which is one of the flow passage caps formed on thesecond flow passage cap plate 362, and therefore the heating-water islocated in the outlet flow passage cap 3622. The outlet flow passage cap3622 includes a heating-water outlet 372, and the heating-water releasedto the outlet flow passage cap 3622 is discharged through theheating-water outlet 372. The heating-water pipe may receive the heatedheating-water through the heating-water outlet 372 and may deliver theheating-water to a main flow passage.

The description of the configuration of the sensible heat flow passageof the first embodiment may be applied to other embodiments of thepresent disclosure and modified examples thereof

Latent Heat Exchanger 40

The latent heat exchanger 40 will be described below with reference toFIGS. 2 and 3. The latent heat exchanger 40 may be disposed downstreamof the sensible heat exchanger 30 based on the flow direction D1 of thecombustion gas. The latent heat exchanger 40 receives latent heatgenerated during a phase change of the combustion gas and heats theheating-water using the latent heat. Accordingly, the combustion gaspassing through the sensible heat exchanger 30 is delivered to thelatent heat exchanger 40, the heating-water flows in the latent heatexchanger 40, and the heating-water and the combustion gas indirectlyexchange heat with each other.

Similarly to the sensible heat exchanger 30, the latent heat exchanger40 may include a latent heat exchange pipe 42 through which theheating-water flows and around which the combustion gas flows. Thelatent heat exchange pipe 42 may deliver latent heat by a phase changeof the combustion gas to the heating-water. The latent heat exchanger 40may include the latent heat exchanger case 41 into which opposite endsof the latent heat exchange pipe 42 are inserted. The latent heatexchange pipe 42 may be formed to be similar to the sensible heatexchange pipe 32, and the latent heat exchanger case may also be formedto be similar to the sensible heat exchanger case 31. Therefore,exceptional characteristics will be described below, but the overalldescription is replaced with the description of the sensible heatexchanger 30. However, a phenomenon may arise in which condensate isgenerated by a phase change of the combustion gas around the latent heatexchange pipe 42 and falls into the condensate receiver 55 by thegravity.

Likewise to the sensible heat exchanger 30, the latent heat exchanger 40may be of a fin-tube type. Accordingly, a latent heat fin 43 is formedin a plate shape perpendicular to the predetermined direction D2 inwhich the latent heat exchange pipe 42 extends, and the latent heatexchange pipe 42 passes through the latent heat fin 43. The latent heatfin 43 may transfer a larger amount of latent heat to the heating-waterby increasing the surface area of the latent heat exchange pipe 42capable of receiving latent heat.

A plurality of latent heat fins 43 may be disposed to be spaced apartfrom each other at predetermined intervals along the predetermineddirection D2 in which the latent heat exchange pipe 42 extends. Theintervals at which the latent heat fins 43 are spaced apart from eachother may be intervals by which condensate formed between the adjacentlatent heat fins 43 is easily discharged. The intervals by which thecondensate is easily discharged refer to intervals between the latentheat fins 43 in a state in which the weight of the condensate formedbetween the latent heat fins 43 is greater than the vertical resultantforce of tensions acting between the latent heat fins 43 and thecondensate. The height of the condensate formed between the latent heatfins 43 is inversely proportional to the minimum interval between thelatent heat fins 43 by which the condensate is easily discharged.Therefore, the intervals by which the condensate is easily dischargedmay be determined by selecting an appropriate height of the condensatedesired to be discharged from the latent heat exchanger 40.

The number of latent heat fins 43 may be smaller than the number ofsensible heat fins 33. Accordingly, the intervals at which the adjacentlatent heat fins 43 are spaced apart from each other may be greater thanor equal to the intervals at which the adjacent sensible heat fins 33are spaced apart from each other. Specific descriptions of the numbersand intervals of the sensible heat fins 33 and the latent heat fins 43are replaced with contents that will be described below in a thirdembodiment. The cross-sectional area of the interior space of the latentheat exchange pipe 42 obtained by cutting the latent heat exchange pipe42 with a plane perpendicular to the direction in which the latent heatexchange pipe 42 extends may be smaller than the cross-sectional area ofthe interior space of the sensible heat exchange pipe 32 obtained bycutting the sensible heat exchange pipe 32 with a plane perpendicular tothe direction in which the sensible heat exchange pipe 32 extends. Thedirection in which the latent heat exchange pipe 42 extends may also bethe predetermined direction D2. As in the description of the latent heatfin 43 described above, by making the size of the latent heat exchangepipe 42 smaller than the size of the sensible heat exchange pipe 32, thelatent heat exchange pipe 42 may have a larger surface area in the samevolume than the sensible heat exchange pipe 32. As the surface area ofthe latent heat exchange pipe 42 is increased, a larger amount of heatmay be exchanged between the heating-water flowing along the latent heatexchange pipe 42 and the condensate.

The cross-section of the latent heat exchange pipe 42 obtained bycutting the latent heat exchange pipe 42 with a plane perpendicular tothe predetermined direction D 2 may have a long hole shape similarly tothe cross-section of the sensible heat exchange pipe 32.

In the first embodiment of the present disclosure, the latent heatexchanger 40 is illustrated as having no means for thermal insulation.However, in various modified examples, the latent heat exchanger 40 mayalso have latent heat insulation pipes (not illustrated) that aredisposed in the same manner as the sensible heat insulation pipes 34.The latent heat insulation pipes may be disposed adjacent to the latentheat exchanger case, and the heating-water may flow through the latentheat insulation pipes to thermally insulate the latent heat exchanger40.

Although the sensible heat exchanger case 31 and the latent heatexchanger case 41 have been described as separate from each other, thesensible heat exchanger case 31 and the latent heat exchanger case 41may be integrally formed with each other as illustrated in the drawing.In this case, an integrated main case 51 including both the sensibleheat exchanger case 31 and the latent heat exchanger case 41 may beconsidered. Accordingly, the sensible heat insulation side plates 312 ofthe sensible heat exchanger 30 and latent heat insulation side plates412 of the latent heat exchanger 40 may integrally form main heatinsulation side plates 512, and the general sensible heat side plates311 of the sensible heat exchanger 30 and general latent heat sideplates 411 of the latent heat exchanger 40 may integrally form maingeneral latent heat side plates 511. Likewise, a first main general sideplate 5111 included in the main general side plates 511 may include thefirst sensible heat insulation side plate 3111 and a first latent heatinsulation side plate 4111 located at the same side along thepredetermined direction D2, and a second main general side plate 5112included in the main general side plates 511 may include the secondsensible heat insulation side plate 3112 and a second latent heatinsulation side plate 4112 located on the opposite side along thepredetermined direction D2.

Hereinafter, a situation in which heat exchangers 30 and 40 of a heatexchanger unit according to another modified example of the firstembodiment of the present disclosure are connected by connection flowpassage cap plates 71 and 72 to form a sensible heat flow passage and alatent heat flow passage connected together will be described below withreference to FIGS. 10 to 14 and 29.

FIG. 10 is a view illustrating the heat exchanger unit according to theother modified example of the first embodiment of the present disclosurewhen viewed from outside the second connection flow passage cap plate72. FIG. 11 is a view illustrating the first connection flow passage capplate 71 of the heat exchanger unit according to the other modifiedexample of the first embodiment of the present disclosure. FIG. 12 is aview illustrating a partial area of a second main general side plate5112 of the heat exchanger unit according to the other modified exampleof the first embodiment of the present disclosure together with flowpassage caps included in the second connection flow passage cap plate 72when viewed from the outside along a predetermined direction. FIG. 13 isa view illustrating a first main general side plate 5111 of the heatexchanger unit according to the other modified example of the firstembodiment of the present disclosure together with flow passage capsincluded in the first connection flow passage cap plate 71 when viewedfrom the inside along a predetermined direction. FIG. 14 is aperspective view illustrating the sensible heat flow passage and thelatent heat flow passage of the heat exchanger unit according to theother modified example of the first embodiment of the presentdisclosure. FIG. 29 is a perspective view illustrating a situation inwhich the connection flow passage cap plates are separated from eachother in the heat exchanger unit according to the other modified exampleof the first embodiment of the present disclosure.

FIG. 12 is view in which flow passage caps 722, 723, 724, and 725 of thesecond connection flow passage cap plate 72 are illustrated by dottedlines on a view of the second main general side plate 5112, straightportions 321, 322, 323, and 324 of a sensible heat exchange pipe 32, andsensible heat insulation pipes 341 and 342 according to the othermodified example of the first embodiment of the present disclosure whenviewed from the second connection flow passage cap plate 72 of FIG. 29along line H-H′ FIG. 13 is view in which flow passage caps 712, 713, and714 of the first connection flow passage cap plate 71 are illustrated bydotted lines on a view of the first main general side plate 5111, thestraight portions 321, 322, 323, and 324 of the sensible heat exchangepipe 32, and the sensible heat insulation pipes 341 and 342 according tothe other modified example of the first embodiment of the presentdisclosure when viewed along line G-G′ of FIG. 29.

In the other modified example of the first embodiment of the presentdisclosure, the latent heat flow passage that is connected to thesensible heat flow passage and through which heating-water flows isformed by a latent heat exchange pipe 42, and the sensible heat flowpassage through which the heating-water flows is formed by the sensibleheat exchange pipe 32 and sensible heat insulation pipes 34. In FIG. 14,the latent heat flow passage is represented in the form of an arrowpassing through the latent heat exchange pipe 42, and the sensible heatflow passage is represented in the form of an arrow passing through thesensible heat exchange pipe 32 and the sensible heat insulation pipes341 and 342. For a better understanding of areas through which the flowpassages pass, the flow passage caps of the connection flow passage capplates 71 and 72 are not illustrated in FIG. 14 in a state in whichgeneral side plates, heat insulation side plates, and fins of the heatexchanger unit are removed. The sensible heat flow passage and thelatent heat flow passage are connected to form an integratedheating-water flow passage. The sensible heat flow passage may include aseries flow passage in at least a partial section, and the latent heatflow passage may include a parallel flow passage in at least a partialsection. In the other modified example of the first embodiment of thepresent disclosure illustrated in FIGS. 10 to 14 and 29, the sensibleheat flow passage is configured to include only a series flow passage,and the latent heat flow passage is configured to include a parallelflow passage.

To form the heating-water flow passage without connection by a separatetube body, the connection flow passage cap plates 71 and 72 connectingthe sensible heat exchanger 30 and the latent heat exchanger 30 may bedisposed in the other modified example of the first embodiment of thepresent disclosure.

To connect openings of the latent heat exchange pipe 42, the sensibleheat exchange pipe 32, and the sensible heat insulation pipes 34 exposedoutside the two main general side plates 5111 and 5112 of the main case(51 of FIG. 2), the connection flow passage cap plates 71 and 72, a kindof a flow passage cap plate, include flow passage caps having, betweenthe main general side plate 511 and the flow passage caps, a connectionspace surrounding the openings.

To connect an outlet of the latent heat flow passage that is exposedoutside a reference side plate, which is one of the two main generalside plates 5111 and 5112, and is formed by the latent heat exchangepipe 42 and an inlet of the sensible heat flow passage that is exposedoutside the reference side plate and that introduces the heating-waterinto the sensible heat insulation pipes 34, one of the connection flowpassage cap plates 71 and 72 that is located on one side along thepredetermined direction D1 includes a connection flow passage caphaving, between the reference side plate and the connection flow passagecap, a connection space surrounding the outlet of the latent heat flowpassage and the inlet of the sensible heat flow passage.

In the other modified example of the first embodiment of the presentdisclosure, the reference side plate is the second main general sideplate 5112, and the one connection flow passage cap plate is the secondconnection flow passage cap plate 72 including the connection flowpassage cap 722. However, the position where the reference side plate isdisposed is not limited thereto.

The connection flow passage cap 722 extends along the flow direction D1of the combustion gas to connect the sensible heat exchanger 30 and thelatent heat exchanger 40 stacked on each other. Furthermore, as theconnection flow passage cap 722 connects a plurality of straightportions included in the latent heat exchange pipe 42 and the sensibleheat insulation pipes 34, the connection flow passage cap 722 may extendinto the latent heat exchanger 40 while extending along the flowdirection D1 of the combustion gas. Accordingly, the connection flowpassage cap 722 that is not completely parallel to the flow direction D1of the combustion gas and that has a portion in an inclined form may beformed.

An inlet flow passage cap 721 having a heating-water supply hole 7211formed therein and the outlet flow passage cap 725 having aheating-water discharge hole 7251 that is the outlet of the sensibleheat flow passage are formed in the second connection flow passage capplate 72. The outlet of the sensible heat flow passage is implemented bythe outlet of the second sensible heat insulation pipe 342. In the othermodified example of the first embodiment of the present disclosure, itis assumed that the heating-water is introduced into the latent heatexchanger 40 through the heating-water supply hole 7211, theheating-water flows to the sensible heat exchanger 30 through theconnection flow passage cap 722, and the heating-water is heated anddischarged through the heating-water discharge hole 7251 from thesensible heat exchanger 30. However, the inlet flow passage cap 721 andthe heating-water supply hole 7211 may be disposed to be connected withthe sensible heat exchanger 30, the outlet flow passage cap 725 and theheating-water discharge hole 7251 may be disposed to be connected withthe latent heat exchanger 40, and the heating-water flow passage may beformed in an opposite direction such that the heating-water passingthrough the sensible heat exchanger 30 faces toward the latent heatexchanger 40.

The plurality of straight portions included in the latent heat exchangepipe 42 may be connected to the inlet flow passage cap 721 in parallel,and the heating-water introduced through the heating-water supply hole7211 may move along the parallel flow passage. The outlet of the secondsensible heat insulation pipe 342 may be connected to the outlet flowpassage cap 725, and the outlet flow passage cap 725 may receive, fromthe second sensible heat insulation pipe 342, the heating-water heatedvia the sensible heat flow passage and may discharge the heating-water.

When it is assumed that a virtual rectangular parallelepipedaccommodates both the latent heat exchanger 40 and the sensible heatexchanger 30, the heating-water supply hole 7211 that is the inlet ofthe latent heat flow passage and the heating-water discharge hole 7251that is the outlet of the sensible heat flow passage may be providedtogether on a reference surface that is one of the six surfaces of therectangular parallelepiped. In other words, both the heating-watersupply hole 7211 and the heating-water discharge hole 7251 may beprovided in a flow passage cap plate that covers one of side platesconstituting the main case (51 of FIG. 1). In the other modified exampleof the first embodiment of the present disclosure, the one side platemay be the second main general side plate 5111 that forms a connectionspace together with the flow passage caps of the second connection flowpassage cap plate 72, and the flow passage cap plate covering the oneside plate is the second connection flow passage cap plate 72.Accordingly, the heating-water is introduced into and discharged fromthe heat exchanger unit through a side surface on which the secondconnection flow passage cap plate 72 is disposed among side surfaces ofthe heat exchanger unit. However, the reference surface may bedifferently disposed without being limited thereto.

As the heating-water supply hole 7211 and the heating-water dischargehole 7251 are disposed in the same side surface of the heat exchangerunit, the direction in which the heating-water is introduced through theheating-water supply hole 7211 and the direction which the heating-wateris discharged through the heating-water discharge hole 7251 may beopposite to each other. As the heating-water is introduced anddischarged through the same side surface, a space required for arranginga heating-water pipe connected to the heating-water supply hole 7211 andthe heating-water discharge hole 7251 may be saved. However, theheating-water supply hole 7211 and the heating-water discharge hole 7251may be disposed in opposite side surfaces.

To locate the heating-water supply hole 7211 and the heating-waterdischarge hole 7251 in the same side surface, the heating-water flowpassage may include an even number of sections in which theheating-water faces from one side to an opposite side of thepredetermined direction D2 or from the opposite side to the one side.That is, the number of times that the heating-water faces from one sidesurface to another side surface of the heat exchanger unit based on thepredetermined direction D2 may be an even number in the entireheating-water flow passage. In other words, when only a change in aprogress direction from one side to an opposite side of thepredetermined direction D2 or from the opposite side to the one side iscounted, the heating-water flow passage may change the direction an oddnumber of times. In the other modified example of the first embodimentof the present disclosure, the entire heating-water flow passage changesthe direction a total of seven times, but the number of times is notlimited thereto. In other words, in the latent heat flow passage and thesensible heat flow passage, the number of sections connecting thereference surface and the surface opposite to the reference surfacealong the predetermined direction D2 may be an even number such that theheating-water flowing from the reference surface to the surface locatedon the opposite side to the reference surface returns to the referencesurface again.

The description of the positions of the heating-water supply hole 7211and the heating-water discharge hole 7251 of the first embodiment may beapplied to other embodiments of the present disclosure and modifiedexamples thereof.

The second connection flow passage cap plate 72 includes the secondsensible heat flow passage cap 723 and the fourth sensible heat flowpassage cap 724 that connect the straight portions 321, 322, 323, and324 included in the sensible heat exchange pipe 32. The second sensibleheat flow passage cap 723 may connect the first outer straight portion321 and the intermediate straight portion 323 in series, and the thirdsensible heat flow passage cap 724 may connect the second outer straightportion 322 and the intermediate straight portion 324 in series.

The first connection flow passage cap plate 71 is coupled to the firstmain general side plate 5111 on the opposite side to the secondconnection flow passage cap plate 72 based on the sensible heatexchanger 30 and the latent heat exchanger 40.

Accordingly, the connection flow passage cap 722 is not formed, and thefirst connection flow passage cap plate 71 includes the latent heat flowpassage cap 722 connecting the straight portions included in the latentheat exchange pipe 42, the first sensible heat flow passage cap 712connecting the straight portions included in the sensible heat exchangepipe 32, the third sensible heat flow passage cap 713, and the fifthsensible heat flow passage cap 714. In FIG. 11, one latent heat flowpassage cap 711 is formed. However, the number of latent heat flowpassage caps 711 is not limited thereto, and a plurality of latent heatflow passage caps 711 may be formed.

The latent heat flow passage cap 711 may be connected with ends of theplurality of straight portions included in the latent heat exchange pipe42. Accordingly, the plurality of straight portions included in thelatent heat exchange pipe 42 may form a parallel flow passage. The firstsensible heat flow passage cap 712 may connect the first sensible heatinsulation pipe 341 and the first outer straight portion 321, the thirdsensible heat flow passage cap 713 may connect the intermediate straightportions 323 and 324, and the fifth sensible heat flow passage cap 714may connect the second outer straight portion 322 and the secondsensible heat insulation pipe 342.

The description of the configuration of the latent heat flow passageincluding the parallel flow passage of the first embodiment may beapplied to other embodiments of the present disclosure and modifiedexamples thereof.

The heating-water flow passage formed by the first connection flowpassage cap plate 71 and the second connection flow passage cap plate 72according to the other modified example of the first embodiment of thepresent disclosure will be described along a flow of heating-water. Theheating-water is introduced into the latent heat exchanger 40 throughthe heating-water supply hole 7211 formed in the inlet flow passage cap721 of the second connection flow passage cap plate 72. As the inletflow passage cap 721 connects the plurality of straight portions of thelatent heat exchange pipe 42 in parallel, the heating-water is deliveredto the latent heat flow passage cap 711, which is formed on the secondconnection flow passage cap plate 72, along the parallel flow passagethrough the plurality of latent heat exchange pipes 42 connected to theinlet flow passage cap 721.

As the latent heat flow passage cap 722 connects the latent heatexchange pipes 42 in parallel, the heating-water is delivered to theconnection flow passage cap 713 through the plurality of latent heatexchange pipes 42 not connected with the inlet flow passage cap 712 andconnected with the connection flow passage cap 713 in parallel. That is,the heating-water flows in parallel in the area of the heating-waterflow passage that corresponds to the latent heat exchanger 40.

The connection flow passage cap 722 is connected with the first sensibleheat insulation pipe 341. The heating-water flows through the firstsensible heat insulation pipe 341 and is delivered to the first sensibleheat flow passage cap 712 of the first connection flow passage cap plate71, and heat loss of the sensible heat exchanger 30 is interrupted.

The heating-water is delivered to the first outer straight portion 321connected to the first sensible heat flow passage cap 712. Theheating-water is delivered to the second sensible heat flow passage cap723. As the intermediate straight portion 323 is connected to the secondsensible heat flow passage cap 723, the heating-water flows along theintermediate straight portion 323 and is delivered to the third sensibleheat flow passage cap 713. As the intermediate straight portion 324 isconnected to the third sensible heat flow passage cap 713, theheating-water flows along the intermediate straight portion 324 and isdelivered to the fourth sensible heat flow passage cap 724. As thesecond outer straight portion 322 is connected to the fourth sensibleheat flow passage cap 724, the heating-water flows along the secondouter straight portion 322 and is delivered to the fifth sensible heatflow passage cap 714. As the second sensible heat insulation pipe 342 isconnected to the fifth sensible heat flow passage cap 714, theheating-water flows along the second sensible heat insulation pipe 342and is delivered to the outlet flow passage cap 725.

That is, the heating-water flows along the sensible heat flow passage inseries. The heating-water is heated by sensible heat while reciprocatingbetween the first connection flow passage cap plate 71 and the secondconnection flow passage cap plate 72 and is delivered to the secondsensible heat insulation pipe 342.

The second sensible heat insulation pipe 342 interrupts heat loss of thesensible heat exchanger 30 while delivering the heating-water to theoutlet flow passage cap 725, and the heating-water is discharged throughthe heating-water discharge hole 7251 and is used for heating.

Main Flow Passage

The condensing boiler 1 including the heat exchanger according to thefirst embodiment of the present disclosure includes the main flowpassage. The main flow passage is a pipe that is directly or indirectlyconnected to a heating flow passage for providing heating and thatsupplies the heating-water to the heating flow passage. The main flowpassage is directly or indirectly connected to the sensible heatexchanger 30 or the latent heat exchanger 40 and supplies theheating-water to the heat exchanger to heat the heating-water orsupplies the heated heating-water from the heat exchanger to the heatingflow passage. Accordingly, the heating-water pipe connected with thesensible heat exchanger 30 and the latent heat exchanger 40 to supply orreceive the heating-water may be included in the main flow passage.

Second Embodiment

FIG. 15 is a vertical sectional view of a heat exchanger unit accordingto the second embodiment of the present disclosure.

Referring to FIG. 15, the heat exchanger unit according to the secondembodiment of the present disclosure may have a sensible heat exchanger81 and a latent heat exchanger 82 having two rows of latent heatexchangers. A first latent heat exchanger 821 located at an upstreamside based on a flow direction of combustion gas may have a greaterwidth in an orthogonal direction than a second latent heat exchanger822.

Furthermore, the heat exchanger unit according to the second embodimentof the present disclosure may have a larger number of straight portions8211 included in a latent heat exchange pipe and a larger number ofstraight portions 811 included in a sensible heat exchange pipe than theheat exchanger units according to the first embodiment of the presentdisclosure and the one modified example of the first embodiment of thepresent disclosure. The number of straight portions that the firstlatent heat exchanger 821 has may be larger than the number of straightportions that the second latent heat exchanger 821 has.

FIG. 16 is a front view illustrating a flow passage cap plate 90 of aheat exchanger unit according to a modified example of the secondembodiment of the present disclosure together with pipes. The pipes areillustrated by dotted lines.

Referring to FIG. 16, the flow passage cap plate 90 of the heatexchanger unit according to the modified example of the secondembodiment of the present disclosure includes a heating-water dischargehole 91 not formed through a flow passage cap and directly formedthrough the flow passage cap plate 90. The heating-water discharge hole91 may not be located downstream of a sensible heat exchange pipe 95along a flow direction D1 of combustion gas and may be disposed on thesame line along an orthogonal direction so as to be adjacent to thesensible heat exchange pipe 95.

The flow passage cap plate 90 according to the modified example of thesecond embodiment of the present disclosure may include a modifiedconnection flow passage cap 92. When the modified connection flowpassage cap 92 is compared with the connection flow passage cap (722 ofFIG. 10) according to the other modified example of the first embodimentof the present disclosure, the length of an inclined portion 922 formedto be inclined with respect to the orthogonal direction and the flowdirection D1 of the combustion gas is smaller than the length of aportion 923 extending along the flow direction D1 of the combustion gasand the length of a portion 921 extending along the orthogonaldirection. Furthermore, when the modified connection flow passage cap 92is compared with the connection flow passage cap (722 of FIG. 10)according to the other modified example of the first embodiment of thepresent disclosure, the width of the inclined portion 922 is smallerthan the width of the portion 921 extending along the orthogonaldirection.

Due to the position of the heating-water discharge hole 912 and theshape of the connection flow passage cap 92, the flow passage cap plate90 may have an asymmetrical structure that does not have line symmetrywith respect to a line parallel to the flow direction D1 of thecombustion gas. The flow passage cap plate 90 may have a tapered shapehaving a decreasing width along the flow direction D1 of the combustiongas. In FIG. 16, a left inclined portion 93 and a right inclined portion94 may be configured to have tapered outer surfaces from differentlocations to other different locations based on the flow direction D1 ofthe combustion gas. This is to reduce a waste of material by cutting aportion corresponding to an unnecessary area.

The shapes of the sensible heat exchanger 81 and the latent heatexchanger 82 according to the second embodiment or the shape of the flowpassage cap plate 90 according to the modified example of the secondembodiment may be applied to other embodiments of the present disclosureand modified examples thereof.

Third Embodiment

FIG. 17 is a vertical sectional view of a heat exchanger unit and acondensing boiler 2 using the same according to the third embodiment ofthe present disclosure. FIG. 18 is a side view of the heat exchangerunit and the condensing boiler 2 using the same according to the thirdembodiment of the present disclosure.

Referring to the drawings, the condensing boiler 2 according to thethird embodiment of the present disclosure includes a combustion chamber20 and the heat exchanger unit.

Furthermore, the condensing boiler 2 including the heat exchanger unitaccording to the third embodiment of the present disclosure includes aburner assembly 10 including a burner 11. The burner assembly 10 and theheat exchanger unit are disposed in sequence along a reference directionD1, which is a flow direction of combustion gas, and components arearranged in the heat exchanger unit along the same direction in theorder of the combustion chamber 20 and the heat exchanger unit.Accordingly, the components of the condensing boiler 2 will be describedbelow in the above-described order of arrangement.

The heat exchanger unit according to the third embodiment of the presentdisclosure, and the burner assembly 10, the combustion chamber 20, acondensate receiver 55, a condensate outlet 53, and an exhaust duct 52included in the condensing boiler 2 using the heat exchanger unit areidentical or very similar to the corresponding components of the firstembodiment. Therefore, descriptions thereof are replaced with theabove-described contents of the first embodiment.

Heat Exchanger Unit

FIG. 19 is a plan view of the heat exchanger unit according to the thirdembodiment of the present disclosure. FIG. 20 is a vertical sectionalview of the heat exchanger unit according to the third embodiment of thepresent disclosure.

Referring to the drawings, the heat exchanger unit according to thethird embodiment of the present disclosure includes a sensible heatexchanging part 300 and a latent heat exchanging part 400. Furthermore,the heat exchanger unit of the present disclosure may include a housing510 that defines heat exchange areas inside by surrounding a sensibleheat exchange area and a latent heat exchange area in which the heatexchanging parts 300 and 400 are disposed.

The sensible heat exchanging part 300 and the latent heat exchangingpart 400 may be disposed in the sensible heat exchange area and thelatent heat exchange area, respectively. The sensible heat exchange areaand the latent heat exchange area may be connected, and the combustiongas delivered from the combustion chamber 20 may flow in the sensibleheat exchange area and the latent heat exchange area along the referencedirection D1 that is the flow direction.

Heat Exchanger Unit—Sensible Heat exchanging part 300

The sensible heat exchange area is an area that is located downstream ofthe combustion chamber 20 based on the reference direction D1 and thatreceives sensible heat generated at the upstream side and heatsheating-water. The size of the sensible heat exchange area is determinedby a space from the most upstream side to the most downstream side ofthe sensible heat exchanging part 300 along the reference direction D1in the space surrounded by the housing 510. Accordingly, the sensibleheat exchange area may be connected with an interior space 22 of thecombustion chamber 20 and may receive radiant heat from the burner 11,and the combustion gas may flow in the sensible heat exchange area.Furthermore, because the sensible heat exchange area has to be able totransfer sensible heat to the heating-water, the sensible heatexchanging part 300 including a sensible heat exchange pipe 320 and asensible heat fin 330 is disposed in the sensible heat exchange area.

The sensible heat exchange pipe 320 is a pipe type component throughwhich the heating-water flows and around which the combustion gas flows.The sensible heat exchange pipe 320 extends along a predetermineddirection D2 in the sensible heat exchange area 32. The predetermineddirection D2 may preferably be a direction perpendicular to thereference direction D1. The sensible heat exchange pipe 320 may extendalong the predetermined direction D2 and may be coupled to the housing510.

The sensible heat exchange pipe 320 may include a plurality of sensibleheat straight portions. The sensible heat straight portions may bearranged to be spaced apart from each other along an orthogonaldirection perpendicular to the predetermined direction D2. The pluralityof sensible heat straight portions of the sensible heat exchange pipe320 may be coupled to flow passage cap plates 363 and 364 of the housing510, which will be described below, to form one sensible heat flowpassage through which the heating-water flows.

The sensible heat fin 330 is formed in a plate shape across thedirection in which the sensible heat exchange pipe 320 extends, and thesensible heat exchange pipe 320 passes through the sensible heat fin330. As the sensible heat fin 330 has a shape through which the sensibleheat exchange pipe 320 passes, the sensible heat exchanging part 300 mayconfigure a heat exchanger of a fin-tube type.

As the sensible heat exchanging part 300 includes the sensible heat fin330, the thermal conductivity of the sensible heat exchange pipe 320 maybe raised. A plurality of sensible heat fins 330 may be disposed to bespaced apart from each other at predetermined intervals along thepredetermined direction D2 in which the sensible heat exchange pipe 320extends. The sensible heat fin 330 may transfer a larger amount ofsensible heat to the heating-water by increasing the surface area of thesensible heat exchange pipe 320 capable of receiving sensible heat.Accordingly, for effective heat transfer, the sensible heat exchangepipe 320 and the sensible heat fin 330 may be formed of metal having ahigh thermal conductivity.

A cross-section obtained by cutting the sensible heat exchange pipe 320with a plane perpendicular to the predetermined direction D2 in whichthe sensible heat exchange pipe 320 extends may be formed in the shapeof a long hole that extends along the reference direction D1. As can beseen in the drawings, the sensible heat exchange pipe 320 according tothe third embodiment of the present disclosure may have a flat shapeformed such that a value obtained by dividing the length of the interiorspace in the cross-section based on the reference direction D1 by thewidth according to the direction perpendicular to the referencedirection D1 equals 2 or more. When the flat type pipe having theabove-described shape is employed for the sensible heat exchange pipe320, due to a wider heat exchange area in the relationship with thecombustion gas, the heating-water may receive a larger amount of heatand may be sufficiently heated even though flowing along the sensibleheat exchange pipe 320 having the same length, as compared with when apipe having a different shape, such as a circular shape or an ovalshape, is employed for the sensible heat exchange pipe 320.

A through-hole through which the sensible heat exchange pipe 320 passesmay be formed in the sensible heat fin 330. The area of the through-holemay be equal to or smaller than the area of the sensible heat exchangepipe 320, and the sensible heat exchange pipe 320 may be firmly insertedinto the through-hole. Furthermore, the sensible heat fin 330 may beintegrally coupled with the sensible heat exchange pipe 320 throughbrazing welding. A method of coupling the sensible heat fin 330 and thesensible heat exchange pipe 320 through brazing welding will bedescribed in detail in the descriptions of FIGS. 15 and 16.

Common louver holes 3303 and 3304 may be additionally formed in thesensible heat fin 330 along the direction in which the sensible heatexchange pipe 320 extends. The louver holes 3303 and 3304 may be formedby punching. The louver holes 3303 and 3304 include a burr raised alongthe periphery thereof. When the combustion gas flows, the burr blocksthe combustion gas to cause the combustion gas to flow around thesensible heat exchange pipe 320, thereby facilitating heat exchangebetween the combustion gas and the heating-water. A plurality of louverholes 3303 and 3304 may be formed. The louver holes 3303 and 3304, asillustrated in the drawings, may include the first louver holes 3303that extend in an oblique direction with respect to the referencedirection D1 and the second louver holes 3304 that are formed betweenthe adjacent sensible heat straight portions of the sensible heatexchange pipe 320 and that extend in the orthogonal directionperpendicular to the reference direction D1. The louver holes 3303 and3304 may be disposed to be spaced apart from each other at predeterminedintervals along the reference direction D1.

The sensible heat fin 330 may further include valleys 3302 andprotruding portions 3301. The sensible heat fin 330 may be basicallyformed to surround the sensible heat exchange pipe 320. The sensibleheat fin 33 may surround areas corresponding to a predetermined widthfrom the peripheries of upstream-side end portions of the sensible heatexchange pipe 320 based on the reference direction D1 such that theareas are distinguished from the remaining areas of the sensible heatexchange pipe 320. Accordingly, between the adjacent upstream-side endportions of the sensible heat exchange pipe 320, the valleys 3302 may beconcavely formed in the sensible heat fin 330 along the referencedirection D1. The areas of the sensible heat fin 330 that are adjacentto the upstream-side end portions of the sensible heat exchange pipe 320relatively protrude to form the protruding portions 3301. Unnecessaryareas are open by forming the valleys 3302, and thus the combustion gasmay more freely flow between the sensible heat fin 330 and the sensibleheat exchange pipe 320.

Heat Exchanger Unit—Latent Heat Exchanging Part 400

The latent heat exchange area is an area that is located downstream ofthe sensible heat exchange area based on the reference direction D1 andthat receives latent heat generated during a phase change of thecombustion gas and heats the heating-water. The size of the latent heatexchange area is determined by a space from the most upstream side tothe most downstream side of the latent heat exchanging part 400 alongthe reference direction D1 in the space surrounded by the housing 510.The latent heat exchanging part 400 that includes a latent heat exchangepipe 420 through which the heating-water flows and around which thecombustion gas flows and a latent heat fin 430 that is formed in a plateshape across the predetermined direction D2, in which the latent heatexchange pipe 420 extends, and through which the latent heat exchangepipe 420 passes is disposed in the latent heat exchange area.

The configurations of the latent heat exchange pipe 420 and the latentheat fin 430 are similar to the configurations of the sensible heatexchange pipe 320 and the sensible heat fin 330. Therefore, descriptionsof basic structures of the latent heat exchange pipe 420 and the latentheat fin 430 are replaced with the above descriptions of the structuresof the sensible heat exchange pipe 320 and the sensible heat fin 330.Accordingly, the latent heat exchanging part 400 may also be configuredin a fin-tube type.

The latent heat exchange pipe 420 may include a plurality of upstreamstraight portions 421 and a plurality of downstream straight portions422 located downstream of the upstream straight portions 421 based onthe reference direction D1. One of the plurality of downstream straightportions 422 may be connected with one upstream straight portion 421among the plurality of upstream straight portions 421. That is, thelatent heat exchange pipe 420 may be disposed in two rows. The latentheat exchange pipe 420 may be disposed to have more than two rows. Asthe latent heat exchange pipe 420 has the plurality of rows of straightportions, the latent heat exchange pipe 420 may improve thermalefficiency that is likely to be degraded when a fin-tube type is used.

In FIG. 20, four upstream straight portions 421 and three downstreamstraight portions 422 are disposed. This is because the referencecross-sectional area of the latent heat exchange area is decreased alongthe reference direction D1 as will be described below. However, thenumber of latent heat straight portions 421 and 422 constituting thelatent heat exchange pipe 420 and extending in the predetermineddirection D2 is not limited thereto.

As the latent heat exchange pipe 420 is disposed in two rows, the latentheat fin 430 may also be disposed to be separated depending on thelatent heat exchange pipe 420. That is, an upstream fin 431 included inthe latent heat fin 430 may be coupled to the upstream straight portions421, and a downstream fin 432 included in the latent heat fin 430 may becoupled to the downstream straight portions 422.

As the latent heat exchange pipe 420 is disposed in two rows, asituation in which the combustion gas fails to sufficiently transferheat to the heating-water due to a deficiency of a heat transfer area inthe latent heat exchange area may be prevented, and as sufficient heatexchange occurs over a wide area for the entire combustion gas, afraction at which the combustion gas is discharged without experiencinga phase change may be reduced.

The cross-sectional area of the interior spaces of the latent heatstraight portions 421 and 422 of the latent heat exchange pipe 420 maybe smaller than the cross-sectional area of the interior spaces of thesensible heat straight portions of the sensible heat exchange pipe 320.Instead of making the cross-sectional area of the latent heat straightportions 421 and 422 smaller than the cross-sectional area of theinterior spaces of the sensible heat straight portions, the total numberof sensible heat straight portions may be made smaller than the totalnumber of latent heat straight portions 421 and 422 such that theproduct of the cross-sectional area of the interior spaces of thesensible heat straight portions and the total length of the sensibleheat exchange pipe 320 remains at a numerical value corresponding to theproduct of the cross-sectional area of the interior spaces of the latentheat straight portions 421 and 422 and the total length of the latentheat exchange pipe 420.

In other words, the latent heat exchange pipe 420 may be formed suchthat in a cross-section obtained by cutting the sensible heat exchangepipe 320 with a plane perpendicular to the direction in which thesensible heat exchange pipe 320 extends, the number of closed curvesformed by the peripheries of the sensible heat straight portions issmaller than the number of closed curves formed by the peripheries ofthe latent heat straight portions 421 and 422. In a case where the samenumber of or more pipes having a larger cross-sectional area than thelatent heat straight portions 421 and 422 are disposed in the sensibleheat exchanging part 300, when the heating-water moves to the adjacentsensible heat exchange pipe 320 via the flow passage cap plates 363 and364, the heating-water may not be efficiently circulated due to a rapidpressure drop in the heating-water that occurs in a section where a flowpassage is sharply bent. Accordingly, the cross-sectional areas and thetotal numbers of the sensible heat exchange pipes 320 and the latentheat exchange pipes 420 are adjusted as described above. The contentsregarding the cross-sectional areas and the total numbers of the heatexchange pipes may be applied to other embodiments and modified examplesthereof. Likewise to the sensible heat fin 330, a plurality of latentheat fins 430 are disposed to be spaced apart from each other atpredetermined intervals along the direction in which the latent heatexchange pipe 420 extends.

One or more layers in which the latent heat fins 430 located in the sameposition based on the reference direction D1 are disposed may be formed.The total number of latent heat fins 430 disposed in the layer mostadjacent to the sensible heat fin 330 among the layers may be smallerthan the total number of sensible heat fins 330.

Referring to the drawings, a total of two layers including one layerformed by the upstream fin 431 and one layer formed by the downstreamfin 432 may be disposed. The upstream fin 431 is disposed in the layermost adjacent to the sensible heat fin 330 among the layers. The totalnumber of upstream fins 431 may be smaller than the total number ofsensible heat fins 330.

The distance by which the adjacent two latent heat fins 430 are spacedapart from each other may be longer than the distance by which theadjacent two sensible heat fins 330 are spaced apart from each other. Toprevent condensate from being easily formed between the latent heat fins430 and hampering a movement of the combustion gas, the interval betweenthe latent heat fins 430 is greater than the interval between thesensible heat fins 330. In the latent heat fin 430, the distance bywhich the adjacent two downstream fins 432 are spaced apart from eachother may be longer than the distance by which the adjacent two upstreamfins 431 are spaced apart from each other.

A predetermined interval at which the adjacent latent heat fins 430 arespaced apart from each other along the predetermined direction D2 may bea distance by which condensate formed by condensation of the combustiongas between the adjacent latent heat fins 430 does not connect theadjacent latent heat fins 430. That is, the distance between theadjacent latent heat fins 430 may be an interval by which condensate iseasily discharged.

FIG. 21 is a perspective view illustrating a plurality of downstreamfins 432 according to the third embodiment of the present disclosure andcondensate W located therebetween. The distance between the adjacentlatent heat fins 430 will be described with reference to FIG. 21, withthe downstream fins 432 among the latent heat fins 430 as an example.

Drops of condensate may be formed and attached to surfaces of thedownstream fins 432. The drops of condensate formed on the surfaces ofthe adjacent downstream fins 432 may be combined to form a large drop ofcondensate W that blocks the space between the latent heat fins 430, andthe combustion gas may not smoothly move along the reference directionD1 due to the large drop of condensate W. Accordingly, the downstreamfins 432 are disposed to be spaced apart from each other at apredetermined interval or more such that the drops of condensate are notcombined with each other and the combustion gas flows between theadjacent downstream fins 432.

Specifically, the interval by which the condensate W is easilydischarged refers to the interval between the adjacent downstream fins432 in a state in which the weight of the condensate W formed betweenthe downstream fins 432 is greater than the vertical resultant force oftensions T acting between the downstream fins 432 and the condensate W.

Referring to the drawing, the condensate W exists between the downstreamfins 432 that are spaced apart from each other by a distance of d andadjacent to each other and that have a width of b in the predetermineddirection D2. At this time, the weight (or, the body force) of thecondensate W formed to a height of h is represented by the product ofthe volume of the condensate W (the distance d×the width b×the height h)and the specific gravity Y of the condensate W. The weight acts on thecondensate in the vertically downward direction.

Meanwhile, the force acting on the condensate W in the vertically upwarddirection is formed by the resultant force of surface tensions. Thedistance d satisfying Equation 1 below is the interval by which thecondensate W is easily discharged, where θ is the angle that a lineextending from the surface of the condensate W forms with each of thedownstream fins 432 and T is surface tension by which the condensate Wis pulled by the downstream fin 432.

γ×b×d×h×g≥2(T×b×cos θ)  [Equation 1]

Here, g is the acceleration of gravity. When Equation 1 above isbalanced under the assumption that other conditions are equal, theheight h of the condensate W and the interval d between the downstreamfins 432 by which the condensate W is easily discharged have an inverserelationship. Accordingly, the interval by which the condensate iseasily discharged may be determined by selecting an appropriate heightof the condensate desired to be discharged from the latent heatexchanger 40.

Tension T measured in one situation is 0.073 N/m. At room temperature,the specific gravity of the condensate is 1000 kg/m³, θ may beapproximated to 0 degrees, and g may be approximated to 9.8 m/s². As theheight h of the condensate mainly ranges from 5 mm to 8 mm, thepredetermined interval d of 1.9 mm to 3 mm may be obtained in the onesituation by substituting the values into Equation 1. The descriptionsof the number of fins and the interval may be applied to otherembodiments of the present disclosure and modified examples thereof.

Heat Exchanger Unit—Housing 510 and Flow Passage Cap Plates 363 and 364

The housing 510 will be described below with reference to FIGS. 17 to20. The housing 510 is a component that surrounds and defines thesensible heat exchange area and the latent heat exchange area and mayinclude a heat insulation side plate 5120 and a general side plate 5110.The general side plate 5110 may include a first general side plate 5113and a second general side plate 5114 spaced apart from each other alongthe predetermined direction D2 and covered by the flow passage capplates 363 and 364. The heat insulation side plate 5120 is aplate-shaped component extending along the reference direction D1 andthe predetermined direction D2. Two heat insulation side plates 5120 maybe disposed to be spaced apart from each other in the orthogonaldirection. Accordingly, the heat insulation side plates 5120 form twoside surfaces of the heat exchanger unit. The lateral shapes of thesensible heat exchange area and the latent heat exchange area aredetermined depending on the shape of inner surfaces of the heatinsulation side plates 5120.

Here, the heat insulation side plates 5120 are used with the meaning ofside plates to which sensible heat insulation pipes 340 are disposed tobe adjacent, rather than the meaning of side plates that reduce theamount of heat transferred to the outside, thereby achieving thermalinsulation. The sensible heat insulation pipes 340 may be additionallydisposed adjacent to the heat insulation side plates 5120. The sensibleheat insulation pipes 34 are pipe type components that are disposedadjacent to the housing 510 surrounding the sensible heat exchange areaand that allow the heating-water to flow therethrough to reduce theamount by which heat of the sensible heat exchange area is releasedoutside the housing 510. As illustrated, two sensible heat insulationpipes 340 may extend in the predetermined direction D2 that is the sameas the direction in which the sensible heat exchange pipe 320 extends.

As illustrated in the drawings, the sensible heat insulation pipes 340may be formed in an oval shape in a cross-section obtained by cuttingthe sensible heat insulation pipes 340 with a plane perpendicular to thedirection in which sensible heat insulation pipes 340 extend.Specifically, the sensible heat insulation pipes 340 may be formed in anoval shape having a long axis parallel to the reference direction D1.The description of the sensible heat insulation pipes (34 of FIG. 2) ofthe first embodiment may be identically applied to the sensible heatinsulation pipes 340 of the third embodiment.

The general side plates 51110 and the flow passage cap plates 363 and364 are plate-shaped components extending along the reference directionD1 and the orthogonal direction. The two general side plates 5110 may bedisposed to be spaced apart from each other in the predetermineddirection D2 in which the sensible heat exchange pipe 320 or the latentheat exchange pipe 420 extends. The two general side plates 5110, whenbeing disposed, may be disposed at opposite ends of the sensible heatstraight portions and the latent heat straight portions 421 and 422. Theopposite ends of the sensible heat straight portions and the latent heatstraight portions 421 and 422 may be coupled through the two generalside plates 5113 and 5114. Likewise, the two flow passage cap plates 363and 364 may be coupled while covering the general side plates 5110 fromthe outside. Accordingly, the general side plates 5110 and the flowpassage cap plates 363 and 364 may form the remaining two side surfacesof the heat exchanger unit that the heat insulation side plates 512 donot cover. Other lateral shapes of the sensible heat exchange area andthe latent heat exchange area are determined depending on the shape ofinner surfaces of the general side plates 5110.

The flow passage cap plates 312 and 313 may include the second flowpassage cap plate 364 and the first flow passage cap plate 363 on whicha plurality of flow passage caps are formed. The second flow passage capplate 364 and the first flow passage cap plate 363 may cover the secondgeneral side plate 5114 and the first general side plate 5113 and may bedisposed adjacent to the opposite ends of the sensible heat straightportions or the latent heat straight portions 421 and 422. Aheating-water supply hole 3710 and a heating-water discharge hole 3720may be disposed in the second flow passage cap plate 364. Theheating-water supply hole 3710 may be an opening through which theheating-water is supplied from the outside to one end of an integratedlatent heat flow passage formed by the latent heat exchange pipe 420 andmay be an inlet of the latent heat flow passage, and the heating-waterdischarge hole 3720 may be an opening through which the heating-water isdischarged to the outside from one end of an integrated sensible heatflow passage formed by the sensible heat exchange pipe 320 and may be anoutlet of the sensible heat flow passage.

The heating-water may be introduced from the outside through theheating-water supply hole 3710 located at a relatively downstream sidebased on the reference direction D1 and may be delivered to the latentheat exchange pipe 420. The heating-water heated in the sensible heatexchange pipe 320 may be discharged to the outside through theheating-water discharge hole 3720 located at a relatively upstream sidebased on the reference direction D1. However, the positions of theheating-water supply hole 3710 and the heating-water discharge hole 3720are not limited thereto.

To connect the outlet of the latent heat flow passage exposed outsideone of the side plates constituting the housing 510 and the inlet of thesensible heat flow passage exposed outside the one side plate, one ofthe flow passage cap plates 363 and 364 may include, between the oneside plate and the one flow passage cap plate, a flow passage cap havinga connection space surrounding the outlet of the latent heat flowpassage and the inlet of the sensible heat flow passage. In the thirdembodiment of the present disclosure, the flow passage cap may be asecond flow passage cap 3642 provided on the second flow passage capplate 364. Accordingly, one of the side plates is the second generalside plate 5112 that forms the connection space together with the secondflow passage cap plate 364. However, the side plate and the flow passagecap plate that connect the inlet of the sensible heat flow passage andthe outlet of the latent heat flow passage are not limited thereto.

The descriptions of the heating-water pipe and the main flow passage ofthe first embodiment may be applied to a heating-water pipe and a mainflow passage that are connected to the heating-water supply hole 3710and the heating-water discharge hole 3720 of the third embodiment of thepresent disclosure.

Shape of Heat Exchange Area Formed by Housing 510

The cross-sectional area of each heat exchange area defined on a planeperpendicular to the reference direction D1 is referred to as areference cross-sectional area. The housing 510 may be provided suchthat the reference cross-sectional area at the most downstream side issmaller than the reference cross-sectional area at the most upstreamside based on the reference direction D1. The housing 510 may beprovided such that at least one section in which the referencecross-sectional area of the heat exchange area gradually decreases alongthe reference direction D1 is formed to allow the combustion gas to flowat higher speed in the latent heat exchange area than in the sensibleheat exchange area.

The housing 510 may be formed to include at least one section in whichthe reference cross-sectional area gradually decreases along thereference direction D1. Accordingly, the heat exchange area may have atapered shape along the reference direction D1 as a whole. As thehousing 510 is formed such that the reference cross-sectional area ofthe heat exchange area decreases, the occurrence of a dead zone whereheat transfer efficiency is deteriorated due to a sharp reduction inflow speed at a specific position when the combustion gas flows in thelatent heat exchange area may be prevented by Bernoulli's principle. Inparticular, in a case where the latent heat exchange pipe 420 is formedof two or more layers as in the third embodiment of the presentdisclosure, the condensate may block the space between the latent heatfins 430, or the length of the latent heat exchange area along thereference direction D1 may become longer, and thus thermal efficiencymay be deteriorated. However, the problem may be overcome because theheat exchange area has a tapered shape due to the housing. Specifically,the housing 510 may be formed to include at least one section in whichthe width of the heat exchange area in the orthogonal directiongradually decreases along the reference direction D1, and the width ofthe heat exchange area in the predetermined direction D2 may be formedto remain constant along the reference direction D1. That is, thereference cross-sectional area is decreased by reducing only the widthin the orthogonal direction in a state in which the width in thepredetermined direction D2 is maintained along the reference directionD1. To form the above-described shape, the general side plates 5110 maybe formed in a general plate shape, and the heat insulation side plates5120 may be formed to be bent as illustrated.

Specifically, referring to FIG. 20, a section corresponding to thelatent heat exchange area is a section from a second point A2 at whichthe inlet end of the upstream fin 431 is located to a point at which theoutlet end of the downstream fin 432 is located. A section in which thereference cross-sectional area decreases along the reference directionD1 in the latent heat exchange area is formed between the second pointA2 and a third point A3 and between a fourth point A4 and a sixth pointA6. A section in which the reference cross-sectional area is maintainedis formed between the third point A3 and the fourth point A4 and betweenthe sixth point A6 and the outlet end of the downstream fin 432.Furthermore, a section between a first point A1 and the second point A2that does not correspond to the latent heat exchange area, but is partof the heat exchange area is also a section in which the referencecross-sectional area decreases along the reference direction D1.

In FIG. 20, it can be seen that the heat exchange area is formed toinclude at least one section in which the width in the orthogonaldirection decreases along the reference direction D1 and at least onesection in which the width in the orthogonal direction remains constant.

Specifically, it can be seen that the width of the latent heat exchangearea in the orthogonal direction decreases along the reference directionD1 in the section from the second point A2 to the third point A3 and inthe section from the fourth point A4 to the sixth point A6. In contrast,it can be seen that the width in the orthogonal direction remainsconstant in the section from the third point A3 to the fourth point A4and in the section from the sixth point A6 to the most downstream sideof the housing 510.

It can be seen that in the section in which the straight portions 421and 422 of the latent heat exchange pipe 420 are located, the width inthe orthogonal direction approximately remains constant and heatexchange is sufficiently performed, and in the section located betweenthe straight portions, the reference cross-sectional area decreasesalong the reference direction D1 to increase flow speed.

The shape of the heat exchange area may be described by defining themost upstream side of each fin 330, 432, or 432 based on the referencedirection D1 as an inlet end and defining the most downstream side as anoutlet end. The housing 510 may be provided such that the referencecross-sectional area gradually decreases from the outlet end of thesensible heat fin 330 to the inlet end of the latent heat fin 430 alongthe reference direction D1. That is, in FIG. 20, the housing 510 may beformed such that the reference cross-sectional area gradually decreasesalong the reference direction D1 in the section from the first point A1at which the outlet end of the sensible heat fin 330 is located to thesecond point A2 at which the inlet end of the latent heat fin 430 islocated.

The housing 510 may be provided such that the reference cross-sectionalarea of the inlet end of the downstream fin 432 is smaller than thereference cross-sectional area of the inlet end of the upstream fin 431.That is, the section between the second point A2 and a fifth point A5includes at least one section in which the reference cross-sectionalarea decreases along the reference direction D1, such that the referencecross-sectional area at the fifth point A5 at which the inlet end of thedownstream fin 432 is located is smaller than the referencecross-sectional area at the second point A2 at which the inlet end ofthe upstream fin 431 is located.

Referring to FIG. 20, the housing 510 may be formed such that thereference cross-sectional area of a partial section of the sensible heatexchange area also decreases along the reference direction D1.

As the width of the heat exchange area is changed as described above,each fin may have a section in which the width in the orthogonaldirection decreases along the reference direction D1.

The area of the sensible heat fin 330 or the latent heat fin 430 in theheat exchange area that makes contact with the inner surface of thehousing 510 may be provided such that the width gradually decreasesalong the reference direction D1 to correspond to a gradual reduction inthe reference cross-sectional area based on the width of a fin definedin a direction perpendicular to the reference direction D1. Referring toFIG. 20, it can be seen that the area adjacent to the outlet end of thesensible heat fin 330 and the width of the upstream fin 431 located inthe section from the fourth point A4 to the outlet end of the upstreamfin 431 decrease along the reference direction D1 depending on the shapeof the inner surface of the housing 510.

FIG. 22 is a vertical sectional view of a heat exchanger unit accordingto a first modified example of the third embodiment of the presentdisclosure.

In FIG. 22, the form of the heat exchanger unit according to the firstmodified example of the third embodiment that has one row of sensibleheat exchange pipes 320 and two rows of latent heat exchange pipes 420as in the third embodiment of the present disclosure may be identified.

A housing 510 b according to the first modified example of the thirdembodiment may also be provided such that the reference cross-sectionalarea at the most downstream side is smaller than the referencecross-sectional area at the most upstream side based on a referencedirection D1.

The housing 510 b may be provided such that at least one section inwhich the reference cross-sectional area gradually decreases along thereference direction D1 is formed to allow combustion gas to flow athigher speed in a latent heat exchange area than in a sensible heatexchange area. Descriptions of effects obtained by the heat exchangerunit as the section in which the reference cross-sectional areadecreases is disposed are replaced with the contents described abovewith reference to FIG. 20.

The housing 510 b may be provided such that the referencecross-sectional area gradually decreases from the outlet end of asensible heat fin 330 b to the inlet end of a latent heat fin 430 b. Thehousing 510 b may be formed such that the reference cross-sectional areagradually decreases along the reference direction D1 in the section froma first point B1 at which the outlet end of the sensible heat fin 330 bis located to a second point B2 at which the inlet end of the latentheat fin 430 b is located.

In the section from the second point B2 at which the inlet end of thelatent heat fin 430 b is located to the outlet end of a downstream fin432 b, a heat exchange area may have only a section in which thereference cross-sectional area gradually decreases along the referencedirection D1 and a section in which the reference cross-sectional areais maintained. Accordingly, the reference cross-sectional area at theoutlet end of the downstream fin 432 b may be smaller than the referencecross-sectional area at the second point B2.

The housing 510 b may be provided such that the referencecross-sectional area gradually decreases from the inlet end of thelatent heat fin 430 b to the outlet end of the latent heat fin 430 b.The housing 510 b may be formed such that the reference cross-sectionalarea of the section from the second point B2 at which the inlet end ofan upstream fin 431 b, which is a kind of the latent heat fin 430 b, islocated to a third point b3 at which the outlet end of the upstream fin431 b is located gradually decreases along the reference direction D1.

The housing 510 b may be provided such that the referencecross-sectional area at the inlet end of the downstream fin 432 b issmaller than the reference cross-sectional area at the inlet end of theupstream fin 431 b. The housing 510 b may be provided such that thereference cross-sectional area gradually decreases along the referencedirection D1 in the section from the second point B2 at which the inletend of the upstream fin 431 b is located to a fourth point B4 at whichthe inlet end of the downstream fin 432 b is located, and the conditionmay be satisfied.

Referring to the drawing, the latent heat exchange area may have asection from the second point B2 to a fifth point B5 in which thereference cross-sectional area gradually decreases along the referencedirection D1 and a section from the fifth point B5 to the outlet end ofthe downstream fin 432 b in which the reference cross-sectional arearemains constant.

The area of the latent heat fin 430 b that makes contact with the innersurface of the housing 510 b may be provided such that the widthgradually decreases along the reference direction D1 to correspond to agradual reduction in the reference cross-sectional area based on thewidth of the fin defined in an orthogonal direction. Referring to thedrawing, the housing 510 b is provided such that the referencecross-sectional area of the section from the second point B2 at whichthe inlet end of the upstream fin 431 b is located to the third point B3at which the outlet end is located gradually decreases along thereference direction D1. Accordingly, a tapered shape may be formed suchthat the width of the upstream fin 431 b defined in the orthogonaldirection gradually decreases along the reference direction D1.

FIG. 23 is a vertical sectional view of a heat exchanger unit accordingto a second modified example of the third embodiment of the presentdisclosure.

In FIG. 23, the form of the heat exchanger unit according to the secondmodified example of the third embodiment that has one row of sensibleheat exchange pipes 320 c and two rows of latent heat exchange pipes 420c as in the third embodiment of the present disclosure may beidentified. The heat exchange pipes of the second modified examplediffer from the heat exchange pipes of the third embodiment in that inthis modified example, the sensible heat exchange pipes 320 c include atotal of five straight portions and a total of six upstream straightportions 421 c are disposed.

A housing 510 c according to the second modified example of the thirdembodiment may also be provided such that the reference cross-sectionalarea at the most downstream side is smaller than the referencecross-sectional area at the most upstream side based on a referencedirection D1.

The housing 510 c may be provided such that at least one section inwhich the reference cross-sectional area gradually decreases along thereference direction D1 is formed to allow combustion gas to flow athigher speed in a latent heat exchange area than in a sensible heatexchange area. Descriptions of effects obtained by the heat exchangerunit as the section in which the reference cross-sectional areadecreases is disposed are replaced with the contents described abovewith reference to FIG. 20.

The housing 510 c may be provided such that the referencecross-sectional area gradually decreases from the outlet end of asensible heat fin 330 c to the inlet end of a latent heat fin 430 c. Thehousing 510 c may be formed such that the reference cross-sectional areaof the section from a first point C1 at which the outlet end of thesensible heat fin 330 c is located to a second point C2 at which theinlet end of the latent heat fin 430 c is located gradually decreasesalong the reference direction D1.

The housing 510 c may be provided such that in the section from thesecond point C2 at which the inlet end of the latent heat fin 430 c islocated to the outlet end of a downstream fin 432 c, a heat exchangearea has only a section in which the reference cross-sectional areagradually decreases along the reference direction D1 and a section inwhich the reference cross-sectional area is maintained. Accordingly, thereference cross-sectional area at the outlet end of the downstream fin432 c may be smaller than the reference cross-sectional area at thesecond point C2.

By more specifically limiting the shape of the latent heat exchangearea, the housing 510 c may be provided such that the referencecross-sectional area at the inlet end of the downstream fin 432 c issmaller than the reference cross-sectional area at the inlet end of anupstream fin 431 c. The housing 510 c may be provided such that thereference cross-sectional area gradually decreases along the referencedirection D1 in the section from the second point C2 at which the inletend of the upstream fin 431 c is located to a fifth point C5 at whichthe inlet end of the downstream fin 432 c is located, and the conditionmay be satisfied.

Referring to the drawing, the latent heat exchange area may have asection from the second point C2 to a third point C3 and a section fromthe fifth point C5 to a sixth point C6, which are sections in which thereference cross-sectional area gradually decreases along the referencedirection D1, and a section from the third point C3 to a fourth point C4and a section from the sixth point C6 to the outlet end of thedownstream fin 432 c, which are sections in which the referencecross-sectional area remains constant.

According to the second modified example of the third embodiment of thepresent disclosure, the inlet end of one of the latent heat fins 430 cmay be formed to be flat without having a plurality of valleys andprotruding portions, like another fin.

FIG. 24 is a vertical sectional view of a heat exchanger unit accordingto a third modified example of the third embodiment of the presentdisclosure.

Referring to FIG. 24, the heat exchanger unit according to the thirdmodified example of the third embodiment of the present disclosureincludes one row of sensible heat exchange pipes 320 e and one row oflatent heat exchange pipes 420 e. The sensible heat exchange pipes 320 einclude four straight portions, and the latent heat exchange pipes 420 einclude six straight portions. However, the numbers of straight portionsare not limited thereto.

A housing 510 e according to the third modified example of the thirdembodiment may also be provided such that the reference cross-sectionalarea at the most downstream side is smaller than the referencecross-sectional area at the most upstream side based on a referencedirection D1.

The housing 510 e may be provided such that at least one section inwhich the reference cross-sectional area gradually decreases along thereference direction D1 is formed to allow combustion gas to flow athigher speed in a latent heat exchange area than in a sensible heatexchange area. Descriptions of effects obtained by the heat exchangerunit as the section in which the reference cross-sectional areadecreases is disposed are replaced with the contents described abovewith reference to FIG. 20.

The housing 510 e may be provided such that the referencecross-sectional area gradually decreases from the outlet end of asensible heat fin 330 e to the inlet end of a latent heat fin 430 e. Thehousing 510 e may be formed such that the reference cross-sectional areais maintained in the section from a first point E1 at which the outletend of the sensible heat fin 330 e is located to a second point E2located downstream of the first point E1 and the referencecross-sectional area of the section from the second point E2 to a thirdpoint E3 at which the inlet end of the latent heat fin 430 e is locatedgradually decreases along the reference direction D1. Accordingly, thereference cross-sectional area does not increase from the outlet end ofthe sensible heat fin 330 e to the inlet end of the latent heat fin 430e.

The housing 510 e may be provided such that in the section from thethird point E3 at which the inlet end of the latent heat fin 430 e islocated to a fifth point E5 at which the outlet end of the latent heatfin 430 e is located, a heat exchange area has only a section in whichthe reference cross-sectional area gradually decreases along thereference direction D1 and a section in which the referencecross-sectional area is maintained. In the section from the third pointE3 at which the inlet end of the latent heat fin 430 e is located to afourth point E4 located downstream of the third point E3, the referencecross-sectional area may gradually decrease along the referencedirection D1, and in the section from the fourth point E4 to the fifthpoint E5, the reference cross-sectional area remains constant.Accordingly, the reference cross-sectional area at the fifth point E5 atwhich the outlet end of the latent heat fin 430 e is located may besmaller than the reference cross-sectional area at the third point E3 atwhich the inlet end of the latent heat fin 430 e is located.

The housing 510 e may be provided such that a first section in which thereference cross-sectional area gradually decreases from the outlet endof the sensible heat fin 330 e to the inlet end of the latent heat fin430 e and a second section in which the reference cross-sectional areais maintained between the most upstream side and the outlet end of thelatent heat fin 430 e based on the reference direction D1 in the areawhere the latent heat fin 430 e makes contact with the housing 510 e areformed. The first section is a section from the second point E2 adjacentto the outlet end of the sensible heat fin 330 e to the third point E3at which the inlet end of the latent heat fin 430 e is located, and thesecond section is a section from the fourth point E4 to the fifth pointE5. The area of the latent heat fin 430 e that makes contact with theinner surface of the housing 510 e may be provided such that the widthof a portion corresponding to the second section remains constant basedon the width of a fin defined in an orthogonal direction perpendicularto the reference direction D1.

Referring to the drawing, the latent heat exchange area may have asection from the second point E2 to the fourth point E4, which is asection in which the reference cross-sectional area gradually decreasesalong the reference direction D1, and a section from the first point E1to the second point E2 and a section from the fourth point E4 to thefifth point E5, which are sections in which the referencecross-sectional area remains constant.

FIG. 25 is a vertical sectional view of a heat exchanger unit accordingto a fourth modified example of the third embodiment of the presentdisclosure.

Referring to FIG. 25, the heat exchanger unit according to the fourthmodified example of the third embodiment of the present disclosureincludes one row of sensible heat exchange pipes 320 f and one row oflatent heat exchange pipes 420 f. The sensible heat exchange pipes 320 finclude six straight portions, and the latent heat exchange pipes 420 finclude six straight portions. However, the numbers of straight portionsare not limited thereto.

A housing 510 f according to the fourth modified example of the thirdembodiment may also be provided such that the reference cross-sectionalarea at the most downstream side is smaller than the referencecross-sectional area at the most upstream side based on a referencedirection D1.

The housing 510 f may be provided such that at least one section inwhich the reference cross-sectional area gradually decreases along thereference direction D1 is formed to allow combustion gas to flow athigher speed in a latent heat exchange area than in a sensible heatexchange area. Descriptions of effects obtained by the heat exchangerunit as the section in which the reference cross-sectional areadecreases is disposed are replaced with the contents described abovewith reference to FIG. 20.

The housing 510 f may be provided such that the referencecross-sectional area gradually decreases from the outlet end of asensible heat fin 330 f to the inlet end of a latent heat fin 430 f. Thehousing 510 f may be formed such that the reference cross-sectional areaof the section from a first point F1 at which the outlet end of thesensible heat fin 330 f is located to a second point F2 at which theinlet end of the latent heat fin 430 f is located gradually decreasesalong the reference direction D1. Accordingly, the referencecross-sectional area does not increase from the outlet end of thesensible heat fin 330 f to the inlet end of the latent heat fin 430 f.

The housing 510 f may be provided such that in the section from thesecond point F2 at which the inlet end of the latent heat fin 430 f islocated to the outlet end of the latent heat fin 430 f, a heat exchangearea has only a section in which the reference cross-sectional areagradually decreases along the reference direction D1 and a section inwhich the reference cross-sectional area is maintained. In the sectionfrom the second point F2 at which the inlet end of the latent heat fin430 f is located to a third point F3 located downstream of the secondpoint F2, the reference cross-sectional area may gradually decreasealong the reference direction D1, and in the section from the thirdpoint F3 to the outlet end of the latent heat fin 430 f, the referencecross-sectional area may remain constant. Accordingly, the referencecross-sectional area at the outlet end of the latent heat fin 430 f maybe smaller than the reference cross-sectional area at the second pointF2 at which the inlet end of the latent heat fin 430 f is located.

Referring to the drawing, the latent heat fin 430 f according to thefourth modified example of the third embodiment of the presentdisclosure may include a pointed portion 4210 f at the mostdownstream-side end thereof. The pointed portion 4210 f is a portion inwhich the width in an orthogonal direction perpendicular to thereference direction D1 decreases along the reference direction D1, and aplurality of pointed portions 4210 f may be provided along theorthogonal direction. The pointed portion may have the above-describedshape such that condensate formed on the latent heat fin 430 f by aphase change of the combustion gas is collected.

The descriptions of the configurations of the housings according to themodified examples of the third embodiment may be applied to otherembodiments of the present disclosure and modified examples thereof.

FIG. 26 is a view illustrating the second general side plate 5114 of theheat exchanger unit according to the third embodiment of the presentdisclosure together with flow passage caps included in the second flowpassage cap plate 364. FIG. 27 is a view illustrating the first generalside plate 5113 of the heat exchanger unit according to the thirdembodiment of the present disclosure together with flow passage capsincluded in the first flow passage cap plate 363. FIG. 28 is aperspective view illustrating all the flow passages included in the heatexchanger unit according to the third embodiment of the presentdisclosure.

Flow passages formed by the sensible heat exchange pipe 320, the latentheat exchange pipe 420, and the flow passage cap plates 363 and 364 ofthe heat exchanger unit according to the third embodiment of the presentdisclosure will be described below with reference to FIGS. 26 to 28. Fora better understanding of areas through which the flow passages pass,the flow passage caps of the flow passage cap plates 363 and 364 are notillustrated in FIG. 28 in a state in which the general side plates 5110,the heat insulation side plates 5120, and the fins of the heat exchangerunit are removed.

Referring to the other modified example of the first embodiment of FIG.29, FIG. 26 is view in which flow passage caps 3641, 3642, 3643, 3644,and 3645 of the second flow passage cap plate 364 are illustrated bydotted lines on a view of the second general side plate 5114, thesensible heat exchange pipe 320, the latent heat exchange pipe 420, andsensible heat insulation pipes 3410 and 3420 of the third embodiment ofthe present disclosure that corresponds to a view of the heat exchangerunit when viewed from the second connection flow passage cap plate 72 ofFIG. 29 along line H-H′. FIG. 27 is a view in which flow passage caps3631, 3632, 3633, and 3634 of the first flow passage cap plate 363 areillustrated by dotted lines on a view of the first general sensible heatside plate 5111, the sensible heat exchange pipe 320, the latent heatexchange pipe 420, and the sensible heat insulation pipes 3410 and 3420of the third embodiment of the present disclosure that corresponds to aview of the first main general side plate 5111, into which the firstconnection flow passage cap plate 71 is inserted, when viewed along lineG-G′ of FIG. 29.

The sensible heat straight portions may form a sensible flow passagethrough which the heating-water flows, and the latent heat straightportions 421 and 422 may form a latent heat flow passage through whichthe heating-water flows and that is connected to the sensible heat flowpassage. The sensible heat flow passage may include a series flowpassage in at least a partial section, and the latent heat flow passagemay include a parallel flow passage in at least a partial section.

As described above, the flow passage cap plates 363 and 364 may includethe first flow passage cap plate 363 and the second flow passage capplate 364. The second flow passage cap plate 364 may have the first flowpassage cap 3641, the second flow passage cap 3642, the third flowpassage cap 3643, the fourth flow passage cap 3644, and the fifth flowpassage cap 3645 formed thereon, and the first flow passage cap plate363 may have the sixth flow passage cap 3631, the seventh flow passagecap 3632, the eighth flow passage cap 3633, and the ninth flow passagecap 3634 formed thereon. The flow passage caps formed on the flowpassage cap plates 363 and 364 are formed in a convex shape toward theoutside of the heat exchanger unit and are connected with the ends ofthe straight portions included in the sensible heat exchange pipe 320 orthe ends of the straight portions 421 and 422 included in the latentheat exchange pipe 420 to allow the heating-water to flow inside. Whenthe flow passage caps of the flow passage cap plates 363 and 364 coverthe general side plates (5110 of FIG. 17), the heating-water flows inthe space formed by the general side plates and the flow passage caps.

The heating-water supply hole 3710 is formed in the first flow passagecap 3641 located at the most downstream side of the second flow passagecap plate 364 based on the reference direction D1. The heating-water isintroduced into the heat exchanger unit through the heating-water supplyhole 3710. The introduced heating-water flows through the downstreamstraight portions 422, each having one end connected to the first flowpassage cap 3641. Accordingly, the downstream straight portions 422 mayform a parallel flow passage.

The heating-water reaches the sixth flow passage cap 3631, to which anopposite end of each downstream straight portion 422 is connected,through the downstream straight portion 422. The opposite end of thedownstream straight portion 422 and one end of each upstream straightportion 421 are connected to the sixth flow passage cap 3631.Accordingly, the heating-water is introduced into the upstream straightportions 421 from the sixth flow passage cap 3631 and flows along theupstream straight portions 421. Accordingly, the upstream straightportions 421 may form a parallel flow passage.

An opposite end of each upstream straight portion 421 is connected tothe second flow passage cap 3642, and the heating-water flowing alongthe upstream straight portion 421 is delivered to the second flowpassage cap 3642. The second flow passage cap 3642 is connected with thefirst sensible heat insulation pipe 3410 and delivers the heating-waterto the first sensible heat insulation pipe 3410.

The heating-water moving along the first sensible heat insulation pipe3410 reaches the seventh flow passage cap 3632 to which the firstsensible heat insulation pipe 3410 is connected. A sensible heat flowpassage in a zigzag form is formed along the sensible heat straightportions arranged in sequence from the seventh flow passage cap 3632 andconnected in series, and the heating-water flows along the sensible heatflow passage from the seventh flow passage cap 3632 to the third flowpassage cap 3643, from the third flow passage cap 3643 to the eighthflow passage cap 3633, from the eighth flow passage cap 3633 to thefourth flow passage cap 3644, and from the fourth flow passage cap 3644to the ninth flow passage cap 3634. In a case where the sensible heatinsulation pipes 3410 and 3420 are arranged as in the third embodimentof the present disclosure, the sensible heat flow passage may beimplemented by connection of the straight portions included in thesensible heat insulation pipes 3410 and 3420 and the sensible heatexchange pipe 32.

The ninth flow passage cap 3634 is also connected with the secondsensible heat insulation pipe 3420, and the heating-water flows alongthe second sensible heat insulation pipe 3420 and reaches the fifth flowpassage cap 3645. The fifth flow passage cap 3645 is connected with theheating-water discharge hole 3720, and the heating-water deliveredthrough the second sensible heat insulation pipe 3420 is discharged in aheated state through the heating-water discharge hole 3720. The entireflow passage in which the heating-water is delivered between thedownstream straight portions 422 and the upstream straight portions 421connected with each other and the heating-water is delivered between theupstream straight portions 421 and the latent heat flow passageconnected with each other is illustrated by arrows in FIG. 28. Theheating-water is heated and discharged while flowing along the entireflow passage.

Hereinabove, even though all of the components are coupled into one bodyor operate in a combined state in the description of the above-mentionedembodiments of the present disclosure, the present disclosure is notlimited to these embodiments. That is, all of the components may operatein one or more selective combination within the range of the purpose ofthe present disclosure. It should be also understood that the terms of“include”, “comprise” or “have” in the specification are “open type”expressions just to say that the corresponding components exist and,unless specifically described to the contrary, do not exclude but mayinclude additional components. Unless otherwise defined, all terms usedherein, including technical and scientific terms, have the same meaningas those generally understood by those skilled in the art to which thepresent disclosure pertains. Such terms as those defined in a generallyused dictionary are to be interpreted as having meanings equal to thecontextual meanings in the relevant field of art, and are not to beinterpreted as having ideal or excessively formal meanings unlessclearly defined as having such in the present application.

Hereinabove, although the present disclosure has been described withreference to exemplary embodiments and the accompanying drawings, thepresent disclosure is not limited thereto, but may be variously modifiedand altered by those skilled in the art to which the present disclosurepertains without departing from the spirit and scope of the presentdisclosure claimed in the following claims. Therefore, the exemplaryembodiments of the present disclosure are provided to explain the spiritand scope of the present disclosure, but not to limit them, so that thespirit and scope of the present disclosure is not limited by theembodiments. The scope of the present disclosure should be construed onthe basis of the accompanying claims, and all the technical ideas withinthe scope equivalent to the claims should be included in the scope ofthe present disclosure.

1. A heat exchanger unit comprising: a sensible heat exchanger includinga sensible heat exchange pipe disposed in a sensible heat exchange areaand configured to receive water and allow the water to flow through thesensible heat exchange pipe, the sensible heat exchange area beingconfigured to receive sensible heat generated by a combustion reactionand heat the water; a latent heat exchanger including a latent heatexchange pipe disposed in a latent heat exchange area and configured toreceive the water and allow the water to flow through the latent heatexchange pipe, wherein the latent heat exchange area is locateddownstream of the sensible heat exchange area with respect to areference direction that is a flow direction of combustion gas generatedduring the combustion reaction, the latent heat exchange area beingconfigured to receive latent heat generated during a phase change of thecombustion gas and heat the water; and a housing configured to surroundthe heat exchange areas to define the heat exchange areas therein,wherein when a cross-sectional area of the heat exchange area defined ona plane perpendicular to the reference direction is referred to as areference cross-sectional area and the most upstream side and the mostdownstream side of the sensible heat exchanger or the latent heatexchanger with respect to the reference direction are referred to as aninlet end and an outlet end, a section in which the referencecross-sectional area is reduced along the reference direction is formedbetween an outlet end of the latent heat exchange pipe and an inlet endof the latent heat exchange pipe.
 2. The heat exchanger unit of claim 1,wherein the housing is provided such that a reference cross-sectionalarea at the most downstream side is smaller than a referencecross-sectional area at the most upstream side with respect to thereference direction.
 3. The heat exchanger unit of claim 1, wherein thesensible heat exchanger further includes a sensible heat fin disposed inthe sensible heat exchange area and formed in a plate shape across thesensible heat exchange pipe such that the sensible heat exchange pipepasses through the sensible heat fin.
 4. The heat exchanger unit ofclaim 1, wherein the housing is provided such that a first section inwhich the reference cross-sectional area is reduced from the outlet endof the sensible heat exchange pipe toward the inlet end of the latentheat exchange pipe and a second section in which the referencecross-sectional area is maintained between the inlet end of the latentheat exchange pipe and the outlet end of the latent heat exchange pipeare formed.
 5. The heat exchanger unit of claim 3, wherein the latentheat exchanger further includes a latent heat fin disposed in the latentheat exchange area and formed in a plate shape across the latent heatexchange pipe such that the latent heat exchange pipe passes through thelatent heat fin.
 6. The heat exchanger unit of claim 5, wherein thesensible heat fin includes a plurality of sensible heat fins, and thelatent heat fin includes a plurality of latent heat fins, and wherein adistance by which two latent heat fins adjacent to each other among theplurality of latent heat fins are spaced apart from each other is longerthan a distance by which two sensible heat fins adjacent to each otheramong the plurality of sensible heat fins are spaced apart from eachother.
 7. The heat exchanger unit of claim 5, wherein the latent heatfin includes a plurality of upstream fins located at an upstream sidewith respect to the reference direction and a plurality of downstreamfins located at a downstream side, and wherein a distance by which twodownstream fins adjacent to each other among the plurality of downstreamfins are spaced apart from each other is longer than a distance by whichtwo upstream fins adjacent to each other among the plurality of upstreamfins are spaced apart from each other.
 8. The heat exchanger unit ofclaim 5, wherein the sensible heat fin includes a plurality of sensibleheat fins and the latent heat fin includes a plurality of latent heatfins, wherein the plurality of latent heat fins form at least one layerin which latent heat fins located in the same position with respect tothe reference direction are disposed, and wherein the total number oflatent heat fins disposed in a layer at the most downstream side withrespect to the reference direction is smaller than the total number ofsensible heat fins.
 9. The heat exchanger unit of claim 5, wherein thelatent heat fin includes, on an end portion at the most downstream sideof the latent heat fin with respect to the reference direction, apointed portion in which a width in a direction perpendicular to thereference direction decreases along the reference direction to collectcondensate formed by the phase change of the combustion gas.
 10. Theheat exchanger unit of claim 1, wherein the sensible heat exchange pipeincludes a plurality of sensible heat straight portions extending alonga predetermined direction, the plurality of sensible heat straightportions being arranged to be spaced apart from each other along anorthogonal direction perpendicular to the predetermined direction andconfigured to form a sensible heat flow passage through which the waterflows, and wherein the latent heat exchange pipe includes a plurality oflatent heat straight portions extending along the predetermineddirection, the plurality of latent heat straight portions being arrangedto be spaced apart from each other along the orthogonal direction andconfigured to form a latent heat flow passage through which the waterflows and that is fluidly connected to the sensible heat flow passage.11. The heat exchanger unit of claim 10, wherein the sensible heat flowpassage includes a series flow passage in at least a partial section,and wherein the latent heat flow passage includes a parallel flowpassage in at least a partial section.
 12. The heat exchanger unit ofclaim 10, wherein based on a cross-section depending on a planeperpendicular to the predetermined direction, a cross-sectional area ofan interior space of the sensible heat straight portion is larger than across-sectional area of an interior space of the latent heat straightportion.
 13. The heat exchanger unit of claim 10, wherein the latentheat straight portion includes an upstream straight portion located atan upstream side with respect to the reference direction and adownstream straight portion located at a downstream side, and whereinthe section in which the reference cross-sectional area is reduced alongthe reference direction is additionally formed between an outlet end ofthe upstream straight portion and an inlet end of the downstreamstraight portion.
 14. The heat exchanger unit of claim 13, wherein basedon a cross-section depending on a plane perpendicular to thepredetermined direction, a cross-sectional area of an interior space ofthe downstream straight portion is larger than or equal to across-sectional area of an interior space of the upstream straightportion.
 15. The heat exchanger unit of claim 10, wherein based on across-section depending on a plane perpendicular to the predetermineddirection, an interior space of the sensible heat straight portion andan interior space of the latent heat straight portion have a shape of along hole extending along the reference direction.
 16. The heatexchanger unit of claim 15, wherein the long hole is formed such that avalue obtained by dividing a length in the reference direction by awidth in a direction perpendicular to the reference direction equals 2or more.
 17. The heat exchanger unit of claim 10, wherein an outlet ofthe sensible heat flow passage and an inlet of the latent heat flowpassage are formed in one of side plates configured to form the housing.18. The heat exchanger unit of claim 10, further comprising: a flowpassage cap plate including, between the flow passage cap plate and oneside plate among side plates configured to form the housing, a flowpassage cap having a connection space surrounding an outlet of thelatent heat flow passage and an inlet of the sensible heat flow passageto fluidly connect the outlet of the latent heat flow passage exposedoutside the one side plate and the inlet of the sensible heat flowpassage exposed outside the one side plate.
 19. The heat exchanger unitof claim 10, wherein the number of sensible heat straight portions issmaller than the number of latent heat straight portions.
 20. The heatexchanger unit of claim 1, wherein the sensible heat exchange pipeincludes a plurality of sensible heat straight portions extending alonga predetermined direction, the plurality of sensible heat straightportions being arranged to be spaced apart from each other along anorthogonal direction perpendicular to the predetermined direction andconfigured to form a sensible heat flow passage through which the waterflows, and wherein based on a cross-section depending on a planeperpendicular to the predetermined direction, an interior space of thesensible heat straight portion has a shape of a long hole extendingalong the reference direction.